Ah cool you guys came round for a look...I was wondering if this was a lost cause...
NVIDIA is most likely your video card . . . . My suggestion would be to reinstall the drivers for your video card and see if that addresses this situation. Methinks it will.
Can you give me a quick over view on how to go about this?....You don't have to go into too much detail....
If it shows up during booting (before the OS loading screen appears) it's hinting at hardware failure, drivers aren't loaded yet at this point. Usually this means that the cooling fan of the video card is faulty. See if it's still under warranty and have it returned / replaced. I'd open the thing up first and see if it is inserted correctly into the slot though.
Note that this assumption of mine is only the case if the error you mentioned indeed appears before the Vista boot screen.
Hmm by the OS loading screen you mean the Windows Logo then yes it does happen before that!...I'll give it a quick look over and see...thanks