High Spec laptop freezing for seconds or two

rockstardmtb Posts 2 Registration date Saturday May 11, 2013 Status Member Last seen May 11, 2013 - May 11, 2013 at 02:38 PM
My laptop (recently bought 2nd hand came by post so kinda gutted) i5 2nd gen, 4 gb ram , 640 hdd, 1 gb nvidia gpu.

problem is it freezes for second or 2 contiguously every minutes. suppose im gonna type dan it will take time , playing music it freezes for second or two n carry on in every 10-20 seconds.. i checked ram.. its fine .. i reformat and installed new os.. checked with all anti virus cleaner and malware softs .. done registry cleaning ..
CPU act normal when i checked with speedfan, process checker and all other utilities..
couldnt find any problem..

what would be the possible problem??