Assuming you're using WinXP, and to some extent with Win2K, when you restarted the computer it probably did its own system restore during the reboot if any errors were present. If the keyboard is working okay after the reboot, I'd advise that you NOT FORCE ANOTHER SYSTEM RESTORE, simply because it's an unnecessary mucking with the system.

During the boot and Windows startup, the system does a verification on many of the system files that are subject to occasional corruption, and does a repair as part of the startup. Doing it again, and interfering with the normal startup is unlikely to help.

A keyboard defect could cause what you saw, and you may want to consider replacing the keyboard if it happens again.

Before you replace it, you could also turn the keyboard upside down and give it a moderate shaking to get some of the pretzel crumbs loosened from the beer stains so they can fall out (or in my case loosen the furballs from the cat that likes to sleep on the keyboard). I would NOT recommend "opening up the keyboard," as closing them back up sometimes is not a trivial operation.

You can check to make sure that the keyboard connector is firmly seated and makes good contact. Carefully unplugging and replugging the connector a few times may clear a bit of crud on the terminals. Small connectors, left plugged in the same position for long periods occasionally get "dirty pins" everywhere except where the contact is made. Any tiny "wiggle" can move the contact onto a dirty part of a pin. Unplugging and replugging "wipes" the pins and often will clean them enough to work just fine.

You can wiggle the keyboard cable to see if there might be an intermittent connection in the wiring inside the cable.

The FIRST ACTION when something unexplainable happens, should be a reboot. If that fixes the problem, even if it's only temporary, don't worry about system repairs until you've eliminated the other obvious stuff (esp. in this case, the hardware).

(And as Stilly suggests: Run your various spyware and malware scans, update your antivirus. Just to be sure there's no extra baggage in there.)¹

In your case, a reboot cleared the problem. You don't normally need to muck with the system when this is the case.

You may want to take a look at language settings, and make sure that you haven't set some program to speak in different tongues.

You can also look at Start|Settings|Control Panel, and double click on Keyboard, look at the Hardware tab and make sure that the system has identified your keyboard as something at least remotely similar to what your keyboard says on its hood ornament.

If there are any loose kids (or other undesirables) around who might have been messing with settings, this is a good time to put them under a bright light and grill them unmercifully. It's unlikely to produce anything that will help with the computer but it's a good teacher/student situation for the kids (or other undesirables).

Try a different keyboard, if you happen to have one handy, and/or try this keyboard on a different machine - if there's one handy. Or, if indicated, get a new keyboard.

¹ On the remote chance that you may have a malware effect, a gratuitous System Restore probably will restore the malware, since it's likely to have been present when recent backups were made. It will also cause your system to make a new backup, and push the oldest previous one out of storage. Do it a couple of times, and all the available backup copies will contain all the errors. Use it when needed, but avoid using it manually unless you have confirmed that it's needed - which usually means you've examined the other reasonable causes for your problem.

John