maybe RAM sticks got fudged up and they just need to be re-inserted.. or the PSU's freaking out?
That would be the first place to look...it cost nothing.
"Generic cheap PSU. " Not good at all.
Try resetting the cmos if you haven't yet.
And yes there's still life in that "old timer" and sadly it probably is at the end of it's life span (at least as far as far as minor upgrades goes).