Was in Skype with my friends while I was playing csgo, then out of no where my computer just shut off, no smell, noise, or anything, computer was running fine all day.
Now, when I go to boot it up, sometimes the fans maybe spin for. half a second, then turns off, no beeping noise, and sometimes the fans don't even spin.

Could this result in a dead Powersupply? or a dead mobo? the mobo is pretty old and is a small thing, but the power supply is pretty new.

450w antec psu
4gb ram
r7850 twin frozr 2gb gpu
i3 2120 cpu

(if those help you, I don't know, felt like I should post them.)

the cpu is some random old crappy one I got out of my old alienware x51.

Thanks.

Google paperclip test and try it out, however it is probably CPU/Mobo related

thats what i thought at first, but me and my dad took his multimeter and tested the power supply and it wasn't sending any power to anything to my computer, so i went to the guy in town and bought a new 600w power supply, hooked it up, bought another 4gb ram and now its all working again. =]

Sounds like you had one of the lower-end antec PSU.

could of been.

It sucks because a lot of people fall into that trap and then you're stuck with a dead psu thinking you got a good one.

I had the same problem with my new computer when I just put it together. I ended up having to RMA the mother board. After a few days they got back to me and said that apparently the MOBO wasn't compatible with my videocard so they offered me another one or full refund. Got a different model and been working fine ever since.

My fans would spin for 1-2 seconds and then boom. Longer if I hadn't tried booting in a while.

either the psu or the mobo

also try to remove the ram, clean it with air and install back.
gl.