Computer shuts off overnight and mobo won't post.

[AncientPC]

Problem pretty self-explanatory. I haven't installed / removed anything hardware / software over the past few weeks. I leave my computer on 24/7/365 and overnight it shuts off and won't boot. I resetted CMOS but that didn't help, not sure what else to try. I don't have any spare socket 939 mobos or CPUs lying around to test.

Mobo is Chaintech VNF4 Ultra with an AMD 64 3000.