The hard-drive activity LED on your computer's front panel flashes when your HDD is active. It blinks reassuringly when you think your system has frozen up -- or it did, when computer cases still had HDD LEDs. Fewer and fewer PCs display HDD LEDs, though most motherboards still support them. No need for hardware mods with Free HDD LED. This portable freeware monitors your HDDs, including SSDs, and displays disk activity in a desktop widget and system tray icon. It monitors SATA and IDE internal drives as well as USB drives, which means it's compatible with most drives, and it works in 32-bit and 64-bit versions of Windows XP, Vista, and 7, which means it's compatible with most systems, too.
Free HDD LED is totally portable, so it runs when you click it; no installer needed. The program displayed a small desktop widget showing our four drives: Our "C" drive, an SSD; Our "D" and "E" drives, a partitioned HDD; and our "F" drive, a USB flash drive. The upper half of each drive's icon flashed red when the drive was active. Hovering the cursor over any of the drive icons displayed its size, free space, file system, and other data. There's also a Donate button that disappears when you do (donate, that is) but we didn't mind it one bit. You can minimize the view to the system tray, where Free HDD LED also displays a single drive (our "C" drive). Right-clicking this icon accesses Free HDD LED's main menu, which let us choose options like auto-starting with Windows, locking the window position, setting transparency, and checking for updates. Check boxes let us choose which of our drives to monitor, and we could also configure the program's refresh rate and disk space warning options, as well as access the program's Web site.
If you wish your PC had a good old blinking HDD activity light as part of its hardware, you can crack open your case and plug one in, if you know how. If that's not an option (it's a bit drastic, we admit) then try Free HDD LED. It's a lot more flexible than a single flashing LED, too.