Keystroke issue can not type all it does is "xxxxxxxxxxxxxx"?

I am trying to help a friend with his computer. He says everytime he tried to type something he get a key "X" that seems like its depressed taking off in a type window. he has unplugged his keyboard and tried another one same things happens. I told him to check all his drivers and they are all up to date?he tried a system restore same problem. He ran virus software no detections.Is this a corrupt .dll system file and will require a OS reinstall?