MY HI GRADE LAPTOP AFTER ABOUT 5 MINS FREEZES?

I HAVE A HIGH GRADE 'VA250D' LAPTOP, IT FREEZES ON THE CURSOR, I HAVE RELOADED IT WITH AN ORIGINAL 'VISTA HOME BASIC' DISC .NO CHANGE .I FITTED IT WITH A TEST SATA HDD AND RELOAD, NO CHANGE, MY IDEA, IS COULD IT BE A FAULTY RAM ,CHIP OR BOARD
DAVID TUCKER, August 2009