I would first uninstall the keyboard, through the device manager, and reboot and let the OS reinstall. If that doesn't do the trick, assuming this is a USB keyboard (?), do the same with the usb host controllers. I doubt the latter, though, if all other USB peripherals are OK, and it is only one key.
Just beware though. When you uninstall the Keyboard, you will immediately loose it's functionality. You will need the mouse to reboot. or a hard reboot from the computer, which may lead into other problems. Uninstalling the USB hosts will be even more problematic and may lead to a restore or reinstall!! The decision will depend on what experience you may have in recovering from such situations.