My brother's computer

Ok.
So my brother was on his Gmail account today, checking his inbox, when his moniter started acting weird. The screen filled with these odd black and white lines, it's hard to explain what it looked like. But it was all black and white with no real pattern to it.
So he restarts the computer and there are more "weird lines". He restarts again, and the moniter says "VGA: No signal", and goes to sleep.
So he restarts again. Now, the whole screen is one solid color, and it cycles through several color, forever. It just cycles through colors. Now however, it just says "VGA: No Signal" again.

So we checked to see if the problem was his computer, or if it was the monitor. We hooked his moniter up to my tower, with my cords, and it worked fine. Then we connected his monitor to my tower, with his cords, and it worked fine. Then we connected my monitor to his computer, and we got "VGA: No Signal".

This seems to indicate that his monitor is fine, and there is something wrong with his tower. We can't get into his computer to find out if he has a virus that might be causing this, because the monitor doesn't show us anything.

We think his video card may have gone bad, or it's a virus.

I wasn't in the room when it started messing up, so I can't tell you what he was doing when it started, but he told me he was just checking his Gmail inbox.
Do you think a scriptkiddie could've caused it?
Or is the video card more likely the problem? Or something else?

Does the bios appear on the monitor properly (ie. before windows starts)? If the graphics are messed up in the bios then it's definitely the video card. Otherwise it could be the video card or it could just be windows fucked up in some way.

graphics card is overheating

maybe fixable,
take it out and see if it's clogged with crud
chances are the fan's ceased up, or the heatsink is full of gunk

You may have to replace it, though
(depending on how hot it's gotten in the past, it may have fried something important)