Odd freezing problem

Geez, it's great to have GFF back again!

I have a Dell GX270 that has been acting really weird as of late. It would suddenly freeze up where it would need a reboot. But then, 85% of the time after the reboot, the computer seemed to start up fine but would seem to hang right before the XP load screenwould show and the monitor seem as if it wasn't connected to the computer (the light went off).

At first I thought something may be wrong with the XP installation, so I did a format and did a clean install. Everything seemed fine for a while, then the problems came back same as before. I then thought the next logical problem would be the actual hard drive. So I replaced that with another I had lying around and did another clean install of XP to just have the same problems.

Anyone have an idea as to what could be causing these problems? I really hope it's not a big issue like the motherboard going bad or something since it's one of those really slim pc's and the innards look very odd to me...I wouldnt' know how to fix it =p

Thanks for the help.

Jam it back in, in the dark.

Yes, both the power supply fan and the fan above the CPU are working. And as for ventilation, the PC has always been kept up on top of a desk and has not had any of the vents blocked in any way. It would make sense to guess that heat is a factor taking the cramped space inside the case, but it's been working fine in that state for a while now.

How ya doing, buddy?