Free USB Guard is an interesting little tool that prevents your system from shutting down if a USB drive or other type of removable drive is still attached. It gives you the opportunity to safely remove the drives or leave them attached and shut down anyway. You can also restart your system or cancel the shutdown. It's portable freeware that can autostart with Windows.
Free USB Guard checks for updates automatically the first time you run it and every time thereafter, unless you uncheck that option in the program's system tray menu, from which you can also check for updates whenever you like.
The first item on the menu is the list of monitored drives. By default, all our removable drives were selected, including our card reader, though none had media. It also listed our internal hard drives by volume, though none was selected. Free USB Guard only detects external hard drives if they're plugged in after the software is running, so we plugged one in, as well as a standard USB thumbdrive. Free USB Guard displayed the external hard drive with the option to deselect it from monitoring. Perhaps unusually, the program didn't let us deselect the USB drive or any of our other monitored drives.
Nevertheless, we shut down the system. Windows 7 displayed the open program warning screen. We clicked Cancel to cancel the shutdown and return to Windows. Free USB Guard displayed a warning pop-up that had buttons we could use to cancel or proceed with the shutdown. We safely removed the drives and proceeded with the shutdown. Our PC shut down normally.
If you always mean to remove a USB drive or other removable drive before you shut down your PC but always forget, try Free USB Guard. It's a simple trick, but one that can really come in handy.