PC shutting down?

[GT98]

Well I've been noticing that my new PC shuts itself off some times when I'm not using it. I normally leave it on all day and night and in the past week I've found it shut off 2 times when I went to go use it. I've checked event viewer to see if I can see if anything ****ed up on there but no luck. Any other suggestions on where to look to see whats shutting it down?

[J1NG]

PSU and related connections.

J1NG

[Elie]

A virus perhaps?

[ZokesPro]

Faulty RAM?
A bios setting?
Did you recently update a driver of some sort?
Spyware?

I have no clue.

[UtwigMU]

Well It's time to play troubleshooting game.

I'd look in PCIe graphic card, power and PSU first, IE try taking out PCIe gfx card and have the system on running something CPU intensive with old PCI graphic card.