Computer won't start

[Khat]

I was given a Gigabyte GA-EP35C-DS3R motherboard a while ago, and just recently gathered the funds to get the ram and a 6 gig core duo cpu (with drives and a box from an older computer) I needed to make a new build.  I've done basic replacements and repairs, but this is my first build from the ground up.

Unfortunately, after hooking it all up, the computer will start, run for a couple seconds and shut down, then repeat the process continuously.  I'm thinking it might be that the power supply I have, a 300 watt, isn't powerful enough to run it.  Does anyone know what I would need, or, if it might be something else?

[patio]

1st suspect is the PSU...2nd suspect on powerup/shutdown issues is MBoard standoffs not in place...and/or thermal paste not applied proper...

[Khat]

Thanks for the confirmation.  The standoffs should be fine, the old motherboard (My dad picked up a virus that fried the bios on it years back) came out and the new one went in using the same ones, and I don't think overheating would be the problem quite that quickly, although that's just my thought.  I have experienced an overheated board before, I've had the system fan on my laptop stop working a couple times.  (Just needed a good cleaning, fortunately)  It, at least, doesn't restart after an overheat.  This one, I hit the power button, the lights come on, the fan turns on, and then it all dies.  And repeat.

I was planning on getting a 6-700 watt psu eventually, (among other upgrades) but it's not in the budget, atm, and I just wanted to get it up and running, cause even at onboard basics, it'll be faster than my old laptop (Poor thing's had a rough life)

[patio]

Borrow a known good PSU and swap it in there overnite to test if it's the culprit...