So I'm having some issues and would really appreciate any help. I recently switched motherboards and ram and it had been running smoothly until today (roughly 2 weeks). I wasn't doing anything intensive, just some homework and it just shut off. The display went black, no signal at all, usb ports got no power, fans still ran, power button did nothing, and I had to power it off completely through the PSU switch. I took out the ram and left in one stick, it turned back on and then shut off after ~30mins. I took it out entirely and replaced the ram with my old ones and it started up, this time it lasted ~1 hour.
I ran the event viewer didn't see anything out of the ordinary (unless I'm not reading it right), ran antivirus (nothing), ran CPU temperature software (27 Celsius).
A little history: Last motherboard died which led to the switch. Tested PSU in the process to see if it was that. Ran the PSU in different setups and it worked (took it to shops/friends, also went out and bought a different PSU to test with the old mobo). But I guess I still wouldn't rule that out.
Mobo: Asus M5A88-M (old one, Asus M4A78T-E)
CPU: AMD Phenom X4
GPU: Asus HD4870
Ram: G.Skill DDR3 1600 12GB(4GBx3) (old one, Corsair DDR3 XMS3 1600 4GB (2GBx2))
PSU: OCZ 700w