Busted power supply?

Sorenson

I built my current desktop around february of 2008, and it's been running real swell so far without so much as a hitch, but this morning it looks like something inside it's finally given up the ghost; last night it began going straight to restarts whenever I tried to put it in sleep mode wwith some regularity (it's done this at random intervals over the years, but very infrequently up until now) and after running it through a virus scan in the hopes it was just some stupid shit at work (there were several hits, but I didn't get a good look since it was like five when I finally hit the sack) I shut it down. When I tried to boot it back up around noon, though, it began to "sputter" so to say, and after doing some internal work to double-check the internal connections (and later on a complete removal and reinstallation of the PSU) it won't even get that far, only giving enough juice to power the monitor and mabe power up the fans and lights for a second when I cut off the power from the back.

I don't know if this is a model-based problem or not, since it's got favorable reviews on Newegg, but the PSU in question's this one.

I wouldn't honestly be surprised if it turns out the PSU was just put through so much that it simply died of exhaustion, but seeing as a replacement is going to run me somewhere in the range of a hundred dollars I want to be absolutly sure this thing is dead before I order a new one. Is anything of the above unusual, or is this just death as usual for a PSU?