How to run Windows 10 on a virtual machine

Test Microsoft's next operating system while keeping your current one.

If you want to play with Windows 10 or Office 2016 but aren't ready to abandon Windows 7 or 8 or Office 2013 just yet, there's an easy solution: a virtual machine. Broadly speaking, a virtual machine (VM) is a sandbox that tricks one operating system into running inside another. If you want a guided tour, check out our review of Windows 10.

Setup requires a more-than-entry-level PC, since you'll be running two resource-hungry OSes at once. But a virtual machine is well worth the effort, because it means fewer headaches than fully upgrading to beta software or running a second version of Windows on a drive partition. Also, if a VM gets a virus or starts acting weird, you can just delete it and reinstall, assuming it doesn't contain any important data.

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There are a number of virtual machine apps you can choose from, but for simplicity's sake, this tutorial sticks to VirtualBox. These instructions are for Windows 7 and 8.1, but you can apply this process to other Windows versions.

What you need:

1. A CPU prepped for running a virtual machine.

2. A broadband Internet connection to download up to 4GB of files.

3. 50GB or more of free space on your PC.

4. Up to one hour of free time.

Step 1: Verify virtual machine support

Oddly, your CPU's virtualization features are often disabled by default. Fixing that can be a hassle, but the process of getting Windows 10 up and running in a virtual machine gets easier after this step. To make sure that virtualization is enabled in your hardware, you need to go into the motherboard BIOS interface. To do that, hit the F2 or Delete key while your PC is booting up. The timing can be tricky if you have a solid-state drive, because your window of opportunity is only a few seconds.

If F2 and Delete don't work, you may need to try F10 or F12 -- your motherboard manual will tell you. If you don't have your manual, you can usually download it from the manufacturer's website. If you don't know who made your motherboard or which model it is, download Speccy and click the Motherboard tab. If you have a laptop, the model is usually printed on the device itself. Then you can Google the motherboard name to find the manual, which will also show you where in the BIOS you will find the setting to toggle your CPU's virtualization settings. Once you've enabled virtualization in the BIOS, press F10 (unless the manual tells you to use a different key) to save your settings and reboot.

You may have a basic BIOS with no CPU virtualization setting. In that case, just hit the Escape key to leave the BIOS and boot into Windows.

Step 2: Download Windows 10 Insider Preview

There are two ways to get Windows 10: (1) install it as an upgrade to your current OS (Windows Vista, 7, or 8.1) or (2) download an ISO file. An ISO is a package of files that's usually installed from an optical disc, but a virtual machine basically tricks your computer into thinking that the files are on a CD or DVD. The virtual machine will install the ISO's contents much faster than an optical drive can. Go to Microsoft's site to get the Windows 10 ISO. Sign up as a Windows Insider, if you haven't already, and choose your file language.

If the Windows Insider ISO is not available, you can grab a 90-day free trial of Windows 10 Enterprise instead. This version won't give you the exact same set of features -- for example, the Windows Store is not present -- but it's the only legit method of getting a free test copy of Windows when the Insider program is not providing them.

Next, select either the 32-bit (x86) or 64-bit (x64) version. If you're not sure which one is compatible with your PC, hold down the Windows key and press the Pause/Break key to bring up the System window. Look for the System type entry, which will tell you if you have 64-bit or 32-bit Windows: 64-bit Windows can use either ISO, but 32-bit Windows can use only the 32-bit ISO. If you plan to test 64-bit software or to dedicate more than 4GB of system RAM to your virtual machine, you'll need 64-bit Windows running on your PC.

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Some older CPUs cannot support a 64-bit virtual machine, even if the CPU is technically 64 bits. If you bought your PC more than five years ago, we recommend Googling your CPU (revisit the instructions in Step 1 to find your CPU name in the System) to check if it has 64-bit guest support. The guest is the OS running inside the virtual machine. The host is the computer the VM is running on.

Step 3: Get your virtual machine software

While your ISO is downloading, you can queue up VirtualBox. Once that's downloaded, install it and set it up for Windows 10.

With the program open, click the New button in the upper-left corner to get started. Name the virtual machine anything you like. The second entry field will default to Windows, if you use that word in the description above it, or you can select Windows from the drop-down menu. In the Version menu, select Windows 10 (32-bit) or Windows 10 (64-bit), depending on which ISO you downloaded.

Now you select your system RAM usage. The green section of the slider is considered safe, and the red zone may cause performance issues. We'd recommend at least 2GB of RAM, preferably 4GB. But if you have only 4GB to start with, give the virtual machine 2GB. If you have 6GB of system RAM, 3GB is great.

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Click Next, and you'll be asked to create a virtual hard drive. You're installing a full operating system, so you'll need a healthy amount of room on your PC's storage device. The default for Windows 10 is 32GB; we recommend at least 25GB to install Windows 10 correctly. Click Create to go to the next menu. If you want to use more or less space, click Hide Description to open an advanced menu with a slider. Click Show Description to return to the hard drive file-type selection. It defaults to VDI, which is fine for basic testing. Other types are compatible with other VM software, such as VMware or Parallels.

Click Next, and you'll see that VirtualBox defaults to dynamic allocation. As the description states, this method will not automatically take up all 32GB (or whatever size you chose). Choosing Fixed size will immediately take up all the drive space that you reserved for the virtual machine. The next window will ask you to confirm the name and size of the VM. Click Create to finish setting up the essentials.

Step 4: Make optional tweaks

The tweaks in this step are optional. All VM apps have customizable settings to improve performance and change how the guest (the virtual machine) interacts with the host (your computer). In the left-hand column of VirtualBox's interface, you'll see the new VM you just set up. It's preselected, since you presumably have no other VMs to choose from right now, so just hit the Settings button to start tweaking. Settings sends you to a General menu, where most options will be grayed out when the VM is running, so you need to set it all up before you've booted it. There are lots of things that you can fiddle with here, but we'll focus on a few highlights.

First, click the Advanced tab to look at how the guest (VM) can talk to the host (PC). If you want to copy and paste between the two, go to Shared Clipboard and select Bidirectional from the drop-down menu. You can also choose your drag-and-drop behavior from the drop-down menu right below that. Since the VM version of Windows can't see the other storage devices and drive partitions on your PC, you'll need drag and drop to transfer files between the guest and the host.

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Now click the System item in the left-hand column. Click the Processor tab to choose how many CPU threads you want to dedicate to the VM. VirtualBox defaults to one thread to stay on the safe side. But if you have more threads in the green zone, you can select them here by moving the slider to the right.

The last point of interest is the Display menu, again listed in the left-hand column. On the Video tab, you can increase how much video memory the VM uses, and you can enable acceleration. (Acceleration can create visual glitches, though, so you must disable it later.) As before, choices within the green zone shouldn't have a negative performance impact on the host PC, unless you're doing processing-intensive tasks while running the VM. Once you've made your selections in the three areas of the Settings menu that we've talked about here, click OK to save your changes.

Step 5: Set up the ISO

Now you're ready to boot your virtual copy of Windows 10. In the left column of VirtualBox, double-click your virtual machine to start it, as if it was a Windows installation disc. VirtualBox will ask for the location of your ISO. Don't remember where you downloaded it? In Google Chrome or Mozilla Firefox, press Ctrl-J to open the Downloads menu. Your downloaded files will be listed in chronological order. In Chrome, click Show in folder. In Firefox, hover your mouse pointer over the ISO and double-click to open its folder.

Want to get fancy? Click the folder location in Windows Explorer and press Ctrl-C to copy the location. Go back to VirtualBox, click the little folder icon with the green arrow, click the location window, and press Ctrl-C to paste the ISO's location. Press the Enter key to go to the ISO's folder. Select the ISO and click Open. If you don't want to try this copy-paste trick, you'll need to manually navigate to the folder containing the ISO.

Once you've set up your ISO location, click the Start button in VirtualBox's main window to run your VM copy of Windows 10. After a few seconds, you'll see a light blue Windows icon on a black background. The ISO is setting up the installer. This may take a few minutes, depending on how speedy your PC is. Then the screen will go black, and you'll see several menus on a purple background. Click the Next button and select Install Now. VirtualBox will tell you about available settings to detect key presses and mouse pointers in the guest (VM). Click the blue-and-white X button in the upper right to make those messages go away. Microsoft will ask you to agree to an end-user license agreement. Check the box if you agree, and click Next.

Step 6: Install Windows 10 in your VM

You have two installation options. Select the Custom option (the second one) and click Next to install Windows in the VM. This step can take a long time, depending on your computer's speed. Our test systems have solid-state storage devices and a dual-core laptop CPU with Hyper-threading, so for us installation took less than five minutes -- a lot faster than installing Windows from a DVD.

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You're almost done! The VM may reboot a few times while it sets up, and then you'll see an operating system setup menu on a white background. You can use express settings here or go through each choice -- you can always adjust these settings later. To do that, finish installing Windows, then click the Windows icon in the lower left-hand corner of the screen, choose Settings, and click Privacy.

In the next section, tell the installer that this PC belongs to you, then sign in with your Microsoft account. Don't have one or don't want to use one? Hit the Sign Up button and choose Connect My Account Later. Now give Windows a username to log in with, decide if you want to set a password, and click Next. (You may get an error right after you click Next, but we clicked the OK button, and Windows kept installing.) Windows will take a few minutes to make some final adjustments in the background, and then you'll finally be on the Windows 10 desktop.

From here, you can do anything you want, but we recommend checking for updates first. To do that, click the Windows icon in the lower left-hand corner, choose Settings in the upper left of the menu that pops up (yes, the Windows Start menu is back), and select Update & Security. This will automatically check for the latest updates for Windows 10.

There's one last optional item you can try: installing Guest Additions (GA) so that you have more aspect-ratio choices for your VM window, or so that you can maximize the VM window and have it automatically scale to the corect resolution for your display. VirtualBox version 4.3.26, which we used for this tutorial, wouldn't scale with GA on our test laptops running Windows 7 and 8.1, but you may have better luck. With the Windows 10 VM running, click the Devices menu at the top of the window, select CD/DVD Devices, and select Remove Disk From Virtual Drive. This disk is just the ISO that you used to install Windows, which you don't need anymore.

Next, in the Devices menu, go to the bottom and select Insert Guest Additions CD image. Windows will pop up a notification in the lower right-hand corner of the screen. Click it and select the first option (the one with the VirtualBox icon next to it). Click Yes, Next, Next again, and Install to start the process. Windows will ask you to confirm some device-driver installations. Click the Install button to do that. The VM's screen may flicker a few times. This is normal. Finally, click Finish to reboot with the Guest Additions installed.

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Step 7: Run Windows 10

You're now done setting up your virtual machine and Windows 10. You can shut down Windows 10 by clicking the Windows icon, selecting Power, and choosing Shut Down. To quickly run the VM next time, go back to VirtualBox's Manager screen, which comes up when you launch the software, right-click your VM in the left-hand column, and choose Create Shortcut on Desktop. That lets you skip the Manager screen and directly boot the VM from your host computer's desktop.

Now that you have a sandboxed version of Windows 10 running inside your main operating system, you can do things like test virus/malware protection or run experimental software without worrying about wrecking your whole system. You can learn how to navigate Windows 10 and decide if you like it before committing to the full upgrade or a fresh installation. You can check out Microsoft Edge, previously known as Project Spartan, which will replace Internet Explorer. Edge is preinstalled in Windows 10 and is supposed to support add-ons intended for Firefox and Chrome, so it's worth checking out. You can use your VM to test the preview version of Microsoft Office 2016, which would otherwise require you to uninstall your current copy of Office first. If you told VirtualBox to use the default 32GB installation of Windows 10, you have about 22GB left over after Windows is installed, so there's lots of room to play in your sandbox.

About Tom McNamara

Tom is the senior editor covering Windows at Download.com.