Windows On-Screen Keyboard

In the rare event you lose your keyboard functionality and youabsolutely need it back, make use of the On-Screen Keyboard from Start
> Accessories > Accessibility > On-Screen Keyboard

Using this application you can type into any application and then reboot your computer to get your keyboard back.

This program has saved me a couple of times when I had to save a document (using Save As) on a remote machine and lost my keyboard functionality.