If it locks up solid, it's probably either a low level driver issue, or a hardware issue and that can just be a bad connection.
I have just cured one such PC, by unplugging all connectors and re-plugging them, and doing the same with all PCI cards and memory modules.
In extreme cases, the best thing is to purchase an exact identical motherboard (on Ebay; always a good place for old computer gear) and just swap it out.