Computer Crashes and Display Won't Come Back On

I'm sorry if this is not a hardware issue, but it seems most likely to me, there is a possibility it could be software though. A couple days ago, my friend brought over a copy of Starcraft, and we were going to verse each other via LAN. While he was setting up the map, I was on a different computer (the one I'm on now) getting ready to install it. From what he tells me, as he was setting it up, the entire computer completely locked up and then restarted.

When he got back to the XP user select screen, he clicked on my name and it crashed again. I went over to have a look at it. This time I turned it completely off. When I tried to turn it back on, nothing would come on my monitor. I restarted a couple times, but the monitor just kept displaying "Video cable connected?" Thinking it was just a monitor problem, I switched monitors to see if it made a difference, it didn't. The same thing happened, only displaying the other monitor's default message of "No signal input".

I switched back the monitors and after a couple restarts, I managed to get a picture, which lasted until I got to the select user screen and it crashed. Again "Video cable connected?". Also, I have two versions of Windows installed on the computer, both are doing the same thing. When I see that I don't have a picture on screen and restart immediately, I can just turn it off and back on, but if I wait for about a minute, I have to hold down the power button for a couple seconds, telling me Windows is still loading even though I can't see it (since one of the versions will load after about 30 seconds if I don't specify which one).

If I leave it alone for a while I can usually get on for a couple minutes, and I can usually stay on as long as I'm very careful to only have one application open at a time. Various graphical glitches when I do get on, as well as problems I had in the past tell me it probably has to do with the video card. A friend of mine made to computer, and a while later I discovered he had overclocked the video card when he put it in. In some cases while playing games, I would get some graphical problems ande sometimes experience crashes similar to what's happening now (but it wouldn't keep crashing over and over again or cause my monitor to stop working).

I found a way around that problem by using ATITool to underclock the video card while I played games. If I lowered the clock too far though, I would experience distortions and crashes similar to the current situation. Like I said, at the time the problem started happening my friend was playing Starcraft, a game that was released back in 1997. I don't see why this would cause a problem since the computer is still fairly new and can still run most current games at their highest, or close to their highest, graphical settings.

Even though it's an old game, I still had ATITool running, mostly because we had been playing Half-Life 2 not long before that and never got around to shutting it off. Ever since it has been crashing at random moments and the screen usually won't come back on until I've given it a few hours. All the graphical glitches and crashes similar to what I've experienced in the past lead me to believe it's the video card, but I don't know nearly as much about the hardware aspect of computers as I do the software aspect so I wanted to get a second opinion.

Sorry if it seemed like I went on and on about small, unimportant details, but since I can't figure out where the problem is even coming from, I figure it's better to say more than what needs to be said than leave something important out. Any help would be greatly appreciated, since the computer I'm typing this on is a piece of crap. If it makes any difference, my computers video card is a Radeon x600 Pro, if you need more information I can post it next time I'm able to get on my other computer before it crashes.

Thanks for your help.

 

I assume you just meant the summary, but I also attached the full scan and the hardware only scan. They had to be compressed because they were too big.

(People should be able to upload .rar files)