The pc was having virus infected os.I formatted it.installed new Os (WIN XP SP2)After installing os when window starts either of the following 2things happens,1- Window starts normally, Desktop & start menu appears & immediatly PC restarts.2- window starts normally, Desktop & start menu appears, but keyboard & mouse doesn't functions.- keyboard keypress is not detected.- mouse moves, but mouse click is not detected.But when this happens PC doesn't restarts.Plz tell me what can be the problem??The pc was not having this problem before installing new os.I have not installed any mouse or keyboard driver.Mouse & keyboard are not wireless.It is PS2 type of mouse & keyboard.Normally windows automaticaly installs driver for it.The PC is having single HDD.The virus due to which i hav formated the pc, was not creating these kind of problems before i formated the pc.these problems were started occuring after formatting pc & installing new OS