Try clear the CMOs on the mainboard using the jumper or removing the battery.

Use the original heatsink that comes with CPU and see if that works!
Hope this helps!
Bill

Just try use 1 256mb RAM on different RAM slot.

Then use the other RAM again the same way, when you reach the system no boot, the RAM connecting to the system is faulty, if certain RAM slot caused...

Adding 1gb RAM and 500GB HDD genrerally may not speed up the system much.

Hugh RAM only shows the diffrent when you run a huge game application or database software, otherwise, 1 extra GB not...

Hi sgamble,

"video card overheating"

Yes, this may be a issue as well.

Check the fan if there is any on the video card.(some may not have the fan design)

If the slower fan with dust...

I would use the other known good HDD to test the system.

Or simply remove the jumper on your HDD to let the system recapture the HDD again.

Before we do have the freezed PC replacing the HDD...

Seems you have done a lot of software part to troubleshoot. If reinstalling the windows still causing the problem, I wonder if you have installed the latest chipset driver for your mainboard and...

Try Last know Good configuration option.

After pressed the power button to power on the PC, press the "F8" key and there will be a boot manual. select from the Last known good configuration" and...