Windows 7 - Non-Win7 hardware issues.

I'm posting here with this type of problem, yet again, because I'm not running Windows 7. I am running WinXP. But if a moderator feels the need to move this to the hardware forum, I'm fine by that.

I am baffled here with this problem. I've done everything in my power to fix it, yet it doesn't do a thing. I have a crappy old laptop, a Dell Latitude D600. I've had many problems with it before, but none are this bad.

From a cold boot, everything will be fine, until about an hour (sometimes less, sometimes more) the computer will suddenly lag horribly. My games show an FPS of 0. I take a measurement, it probably takes 3 seconds to render a single frame. It doesn't just happen on games, though. It happens on anything I do. Watching a video, browsing low-resource sites, it's even happened while I used Paint. From a warm boot, it takes only 5 minutes.

I have nothing else memory or processor intensive running in the background. At the time of the slowdown, I open the task manager and nothing has changed, which leads me to believe it's a graphics issue. But I've updated the drivers on my card, and it still lags.

The funny thing is, about a month ago, this was never happening. This laptop's been taken much better care of than my previous laptop of the same model (which is now defunct). That laptop, despite a lot of abuse, has never had this issue.


So.. bottom line is, I believe it's a graphics issue and I need to fix it or else my productivity's going to go to hell. I can't buy a new laptop. Is there anything I can do to fix it?
(side notes: I can't check the temperature of the GPU, but it can't be anywhere near the temperatures that my old laptop were running at, and it ran my games and other programs with no problem whatsoever.

Thanks for any solutions you may give me.