Graphics cards scramble/crashing problem...

My friend has had his PC for 7 months, but several days ago, the screen will scramble instantly, typically during games. It has a Connect3D X800GTO.

I noticed that it did it when the temperature of the GPU was high using ATi Tray Tools, and would crash during a benchmark test. Bearing in mind, this problem arised at the start a series of hot days here in Nottinghamshire, UK. And, the PC isn't the best of cases for gaming and stuff. When the screen scrambles, I can still recognise the desktop and move the scrambled cursor graphic around, but after a few seconds, it turns itself off.

Yesterday, it started doing it much sooner, and would often do it before even finishing loading Windows, and then eventually, would do it from the momet I turn it on.

So I decided let it cool down, and it would this time let me get as far as loading Windows up, but then scrambled/crashed again.

I took the graphics card out put it in another PC and it did the same thing, so it's definitely the graphics card. The graphics card was very dusty, bu I've cleaned it now.

I think the card maybe on its way out, but I hope it isn't. Any ideas for solving the problem?

 

I looked the the graphics card from the top and it there's about a 1mm gap between the heatsink and this big chip which I assume is the processing core.

Actually, looking at it again, there's something on the middle of the processing core, taking up a large amount of it, which may be dust/muck, or may be part of the processing core.

I have no idea myself. Any help will be appreciated.