strange things

when i turn my pc on and after everything as finished loading up,a strange thing as started happening.As soon as i click on anything,icons on the desktop start pulsing and i hear a fast clicking sound coming through the speakers and i can't cannot open anything while this is happening,but when i use the ctrl alt and delete buttons to get the task manager up it stops and everything is fine.can anyone tell me whats going off?any iders would be much appriciated.I am running xp prof

 

sorted it.new keyboard i bought,changed for another and its cured it,thats the second one in as many weeks,same make.Is that common