Mabye overheating?

Hi, i have run out of ideas to see what is wrong with my PC, thought it might be good to see if any of you can suggest anything. First my computer froze when i was playing games, my friend suggested overheating/dead graphics card, i replaced this and the promblem carried on. Now it seems to freeze if i am doing to much mainly when watching videos on youtube and when updating my ipod. Any suggestions?

I've been having the same problem as well. Do you have a SATA harddisk? Check to see if the SATA harddisk isn't getting disconnected on and off every time.