i dont think it might be caused by hardware. It can be caused by software incompatibility. I once have a similar problem with my notebook. Every now and then it just freezes but just for a fraction of a sec. Can see it when moving the mouse it suddenly stops a while. Very frustrating. I later found out that the XP wireless thinge causes the problem. Install the correct driver and software and walla! Problem solved! It was problem with my inspiron 600m notebook.

why not trying to format ur pc 1st before buying new hardwares... might solve the problem