Checking NVRAM then hanging ....

Hello all .... I hope someone here can help me ....

I know my way around the operation of a PC well, and Im familar with all of the components, but Im having a problem that I currently dont understand

I picked up a PC off of Fleabay ... its a 3gig P4 prescott, with a more generic Mobo w/ integrated graphics and such. I can look up the MB model number if that becomes important ....

The past two nights, I have come home to find my PC off, and it hard to turn back on.

I have to turn it off and on several times to get it to boot fully, When it doesnt boot, I get the usual beep, and it hangs on the booting screen Saying "Checking NVRAM" .... I restart it, untill it finally boots up, then works perfectly fine ... no slow speeds or anything

Tonight though, Oddly my PC would not even try to come on the first few times I pushed the power button ..... I unplugged the power cord, and plugged it back up, and when I did so I got power, but still had to cycle the power off and on a few times to get past the "checking NVRAM"

Im inclined to say that its either the MB or the Power Supply .... but I have no way to narrow it down fully.

I have a PS from an old Gateway laying around, I could try to put that in (And plug only the hard drive up so as to minimize current draw)

Any thoughts or suggestions would be appreciated

***EDIT ... I would like to add that Ive had this PC running for 3 months with no problems, untill recently .....