PC strange coloured pixels cant boot into windows

Hi,
I am new to this forum, and I know a little about computers but not a great deal.
Anyway, here's my problem.
A few days ago, when i was playing a computer game I got the message 'xxx driver has stopped working and has successfully recovered'. The monitor then flashed black for a bit and then stopped working so I had to reboot and it ran fine after that. It had happened to me before, so I didn't think much of it.

But, the next day when I went to turn on my PC, there were coloured pixels sprawled accross the screen in a pattern. For the screen where it loads the mobo stuff (for me where it says Asus Lifestyle and shows the logo etc), there are purple, yellow and white pixels in a pattern all accross the screen.
Then, when it does the 'checking Nvram... ' some of the words are missing and some are squiggled up.
As it loads into windows, there are red pixelated lines running down the screen. After that the PC just automatically restarts.

Now the funny thing is, on the first day, it wouldn't boot into windows at all. Then, I waited a day and it booted into windows fine, but after a few minutes in the desktop screen red pixels started to flash on the screen and sometimes the BSOD would appear.
But today I can't even make it boot into windows.

PC specs:

CPU: Intel Core 2 Duo 2.66Ghz
Graphics: Nvidia 8800Gtx
Mobo: Asus P5K Premium
Ram: 4GB PC-6400 Geil Black Dragon
All bought about 1 and 1/2 years ago.
I have a Mirai 19" monitor as well, but that's not the problem, as I have tried it with another monitor and still the same problem.

Has anyone had a similar problem, or knows what the problem is?

Thanks in advance.

Hmm. okay thanks. I'll try to take out a stick of ram at a time maybe and boot each time?
Also, what do you mean by 'corrupted post data'?

Thanks

Seems the fastest way to troubleshoot this one is to throw in a different video card. If it works as normal (3d stress test, benchmark, etc) then your mobo and RAM is okay and your 8800 GTX is fried (maybe). If you have another system (or a friend in the local computer shop) to check the 8800 GTX, you'll know then for sure.

As a direct replacement look at the 1Gb HD4870 or GTX260, their performance is equal
overall and you should have no problems finding either under budget.
If your screen is 1280x1024 you could save some cash and seek the 512Mb HD4870.
You have given prices in Pounds so here are a few places in the UK to look: Scan,
CCL, Novatech, Overclockers, Ebuyer and Pixmania.