freezing help, overheated cpu?

The PC is my familys pc, its something along the lines of an amd xp 2600 w/512 stick of ddr and a geforce3. I built it using parts that I had around and a few new ones probably almost a year ago now.

So the problem: Turn computer on, it'll get to desktop. Let it sit for ~20 minutes and it'll lock up and you get horizontal lines across the screen. If you reboot it, it either won't turn on at all (which suggests overheating and the motherboard protecting you from turning it on while its too hot) or it gets to like the windows loading screen before it locks up and the screen gets a bunch of horizontal lines on it again.

My first assumption was that the video card was shot, so I replaced it with my sisters and that didn't do it. Then maybe I thought it was bad memory, so I tried that without any success. I don't have any other identical motherboards to make any kind of swap to see if its the proccessor or motherboard specifically, but thats really the only other thing to check. Its obviously not the hard drive, and I've checked the other major components.

Assuming that the proccessor fan is 100% void of dust and the case is sufficiently cooled, can anyone think of stuff to try before completely replacing the motherboard and processor? That would really be a PITA Going to post this to a couple forums I visit to see if I can get any good suggestions, thanks for any possible help =)

see if there are any puffy or leaking capacitors on the motherboard.

Other than making sure that the fans are spinning, the heatsink is seated correctly, and the voltage is set right, you could try maybe underclocking and/or undervolting the system so that it doesn't get as hot. And there's always the old test of take off the side panel and aim a big house fan at the open case.

<font color=red> یί∫υєг ρђœŋίχ
<i>The devil is in the details.</i></font color=red>
@ 192K -> 200,000 miles or bust!

If you get MBM5, then make sure you enter the correct mobo or you may get inaccurate readings.

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<font color=red>You're a boil on the arse of progress - don't make me squeeze you!</font color=red>

You'd think that with the underclock (for stability and quiet) that likely goes into a lot of Dells that you wouldn't run into too many heat problems...

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<font color=red>You're a boil on the arse of progress - don't make me squeeze you!</font color=red>

Gotta love the minimalist PSU stance. Squeezing every bit of savings out of each sell they make. Try to upgrade later and then run into stability problems because of a lack of power.

What changes have you made to increase the W draw?

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<font color=red>You're a boil on the arse of progress - don't make me squeeze you!</font color=red>

ROFL! How can you be so brutal to your nice little Dellie? Shame on you.

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<font color=red>You're a boil on the arse of progress - don't make me squeeze you!</font color=red>

All that being said - there are still people who should only be allowed to have a Dell or other major OEM. There aren't enough people like us in the families across the nation to take care of all the family PCs. That tech support "blanket" is critical to them maintaining sanity.
The better option is a good local PC shop, but not every city/town has a good one and the cities with good ones still don't have 24hr tech support. As much as I don't like them and some of the products that they put out, they do serve a purpose.

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<font color=red>You're a boil on the arse of progress - don't make me squeeze you!</font color=red>