OP, I said that I was guessing. Check you PSU with a DDM(digital multi-meter).
PSUs can have intermittent problems that are very hard to diagnose but since your power
light is blinking all the time, just take readings off all the rails, 3.3, 5 and 12V while the comp
is under load. See what you got. NFG=no f-ing good.
I would check the PSU voltages first. You just need an ATX PSU. A really good Fortron or Sparkle
can be bought for around $60-$80 shipped.
There are cheaper Fortrons but for $20 why bother, that's my attitude.
Three weeks ago I bought a Zippy/Emacs HG-2 6400P for $100 to the house.
You can't order today anyway, so give it a day or two and you will get more imput.
Do a search for PSUs here at Anandtech, they have been talked to death.
...Galvanized