I’ve “fixed” such a computer a with tendency to freeze today. It happened that about every two hours, the computer froze. I let it roam for a while, and noted that the Chipset’s North-Bridge was getting terribly hot. The computer chassis was left open because of driver incompatibility regarding the on-board network interface, so a PCI based NIC was added. However, the PCI NIC was not Small Form Factor (SF), which forced them to leave the computer chassis open.
The model is this one, and if you don’t want to burn it, leave its chassis closed at all times.