P.C. starts on it's own!

Hi, A problem Ihave not been able to solve: P.C. is off. move or knock the keyboard and the P.C. boots.
now even though the P.C. is off the keyboard light is on. (wife noticed this morning)so I pressed a few keys.
P.C. did not start. It's temperatemental, if one accidently knocks/moves the keyboard when the P.C. is off it boots. any sugestions? windows XP. ps2 connector. foxconn motherboard thanks
john