I'm going to assume you used PS/2 keyboards. Here are several things you might want to know:
1) Unlike USB keyboards, PS/2 keyboards are NOT hot-swappable. You can't just plug in one onto a working computer and expect it to work right then and there - you need to switch the computer off, plug in (or plug out) your keyboard, and turn the computer back on.
2) If you plugged/unplugged the keyboard while the computer was powered, there is about 10% chance that the keyboard will work right off the bat, without the computer being power cycled. In most cases, keyboard will not run and will appear dead (and that's the least of your worries).
3) While we're at plugging keyboards onto a working PC, keep in mind that plugging anything onto a powered and running PC, other than audio cables and USB is a great way to release the magic blue smoke.
Edit: If some of the keyboards you were tesing had something shorted out in the circuitry, it could have damaged your computer's mainboard. Does your keyboard work before Windows loads; i.e. can you enter BIOS setup? Do you have a spare USB keyboard lying around you could try?
Edit2: Can you try your original keyboard on a different PC? Do ANY keboards work with your computer right now?