Is this video card to blame?

Problem description: XP refuses to boot up and during the post screen text is garbled and there are vertical green lines going down the screen.
Attempted fixes: This is a friend's PC. At first I was able to boot into Windows and the problem was the garbled text and the PC crashing whenever he played a game for more than a few minutes. I checked the temps on his 7600GT and they were **** hot! it reached 100C before I decided to turn off the video card stress program. I looked inside the PC to see it caked in dust. I gave it a good blow and instructed him to go buy a can of compressed air from Maplin. After this the temps dropped to a more respectable 70C on load and the PC no longer crashed, the lines on the screen had also disappeared.

But a few hours later after some heavy gaming it started to play up again and now no longer boots into XP unless it is in safe mode. I'm presuming that the video card is bust but I just need some reassurance.
Recent changes: He hasn't done anything to the system he literally only plays Drift City. It's a black box to him.
Operating system: Windows XP, fully updated.
System specs:
Asus M2N motherboard
AMD 6000+ CPU
nVidia 7600GT
No idea what the power supply is, but it is rated at 400W and has 18A on the 12V rail. I'm also thinking that the power supply may also be a contender for the **** up as it's pretty old.
I have Googled and read the FAQ: Yes

When I say the text is garbled I mean that the text is readable but the "|" key keeps appearing behind the letters. A screen shot will describe it better than I ever could.

Here is a pic showing the lines:
http://img.waffleimages.com/563649 [...] C00629.JPG

Here is a pic showing the text (sorry about the quality, I had less than a second to snap the pic and the phone takes ages to take a pic):
http://img.waffleimages.com/24e05a [...] C00631.JPG