EMO-TOCROSS

Just put together a decent gaming computer for my friend, and we are having issues with something I would describe as "tearing."

Basically he'll be running a game, say world of warcraft for example, and when he hits the Windows button, the game starts to immediately "tear" and lags up the computer for a while until a window opens, then when you try to open another window the game "tears" again and lags up the computer while in the background. Does this sound familiar at all? It's hard to explain/describe.

I was wondering what could be causing this. I've tried putting my Video card into his, and it does the same thing for him, so I don't think its the card. All his drivers are fully updated. Could it be the SATA/Raid harddrive (this was the first time I did SATA/Raid instead of IDE), or ram? processor? It makes no sense to me, i've never seen this before.

Let me know your thoughts, thanks!