This morning my computer (XP) worked fine. Suddenly the keyboard stopped responding. Num Lock, Scroll Lock, and Caps Lock lights flash continuously. Everything else on the computer is fine. All programs work, display is normal, mouse works, internet works, USB peripherals work. Reboot didn't help. Unplugging and rebooting didn't help. Changing keyboards didn't help. Plugging keyboard into another USB port didn't help. Restoring computer to last Monday didn't help. Flashing of lights begins about 1/3 through boot sequence. Useless Windows Control Panel/keyboard/Properties dialog box says "This device is working properly". Windows finds no updated driver. Troubleshooter is as usual useless.

See if you can get into the bios, and use the keyboard there.

Most computers its either Esc, F1 or Del.

Wait, hold on, I just remembered something.

I was reading something about static charges a while back, and some cache or something...

Anyway, unplug the power and hold the power button for 30 seconds-ish. When you're done, start it back up and post what happens.

The long answer: I reseated the RAM chips, since that has been suggested on other web posts. I tried booting to safe mode. Oops, no keyboard to tell it. I booted using the Dell startup disk. I then had to choose boot from HD or disk. Oops, no keyboard to choose. I got a [DOS] message there was no FAT partition on drive C. That couldn't be good. After several more re-boots, I got a DOS window with a D: prompt. I checked dir, and there wasn't much, certainly less than I knew was there. I switched to C: (notice the keyboard is now working in DOS) and did a dir, and there wasn't much there, either. When the computer tried to boot Windows (auto after 30 seconds) the keyboard light flashing started almost as soon as it passed DOs and hit the Windows loading. It did this circle repeatedly. I next switched to the Dell "reinstall Windows" disk. It copied files, then hung up at the "starting Windows" message. (a reason I love Windows so much) I shut down and restarted with the reinstall Windows disk. Windows came up normally and the computer is now exactly as it used to be - all programs running, desktop as usual, keyboard working. I'm afraid to shut it down and try a restart, but for now, after doing essentially nothing, it works. Thanks for your suggestions. I'll remember them and try if it happens again. Hopefully not...

I know this forum is over a year and a half old but I ran into the same problem running windows 7. My computer freaked out one day and wouldn't start up because it said no keyboard detected. The three lights (num lock/cap lock/scroll lock) were flashing and no keys were working. So, I tested the keyboard on my laptop... worked... This was the second forum I looked at and I went with the most simple solution first (the solution posted by InfoJunkie4Life). Unplugged my power supply and held the power button in for ~30 seconds. Plugged everything back in, including my keyboard, and started my computer. Well... that fixed my problem!

So, thanks InfoJunkie4Life... made my life a lot less stressful!