Ok yesterday i opened up my pc and noticed that one of the memory heatsinks had nearly fallen off. I fixed this with a thermal pad of the old cooler whilst i wait for some new thermal tape. So my pc was working perfectly yesterday but then this morning whilst playing race driver grid the game just froze but not my pc. After about 15-20 seconds it worked again. I then tried playing the Demigod demo and after about every 30seconds the game locks up. I cant work out if the problem is my GPU or somthing elce. When i now load up GRID it takes an age and my hard drive light it flashing slowly and dimly as if the hard drive just isnt reading the data very fast. Also my pc is fine to use normally i can still play EVE Online fine and surf the web with no problems. Any ideas?