Try going into Safe Mode by restarting your pc. As it's restarting press the F8 key and use the down arrow to select Safe Mode. Does the keyboard work properly in Safe Mode ?If not try opening Device Manager by typing dev in the Start Menu's search box Click where it say Keyboard in Device Manager and right-click on your Keyboard and select uninstall and restart your pc. When you get to the logon screen don't try to logon, instead with your mouse click on the red thing in the lower right corner's up arrow and click on restart computer. Now go back into Safe Mode, Windows should reinstall your keyboard drivers in Safe Mode while your antivirus isn't running. If it doesn't re-open Device Manager , expand any of the hardware items, click on Action and then click on Scsan For Hardware Changes. That definitely will reinstall the driver. If you have an after market i/e: Logitech, etc., you may need updated drivers for it. If it's a wireless keyboard try re-syncing it or replacing it's batteries. Also make sure it's PS2 plug or USB 2.0 plug is fully plugged in. For PS2 keyboards/mice make sure your pc is turned off before messing with it's cables. It also could just be that you need a new keyboard. I believe Walmart has them for aroung $15.00 or so. Radio Shack has keyboards also. Try scanning for malware in Safe Mode. Do a full scan in Safe Mode to be sure.