my guess would be the memory , i once had the same problem after putting in a faulty stick of memory
if your not technicaly minded i recomend park computers in blackburn on darwen street , give them a ring and ask how much to test your pc , it wont be much
DO NOT i repeat DO NOT take it to any pc world so called service center you will just get ripped off/over charged to hell
if your pc is under warrenty then take it back to where you bought it
