Key board & mouse not working while computer

Hello,

My computer boots ok straight to window XP every time it is turned on. Keyboard and mouse are not responding at all from the beginning. I can not interupt to do any thing by using key board and mouse ( no led lights from the time PC on )
I wont be able to use any key to go to del to setup or F8 for safe mode. I am afraid either CPU or mother was bad.

Please give me some advise

Thanks

Mike T