I've personally seen < 9.5V with 60% rated load on +12 and nothing on +5/+3.3.
I've been running into this a lot lately, I wasn't aware it was a problem at all but it could explain the odd locks I get every once in a while.. my multimeter vanished so i'm waiting for a new one in the mail to check this out
If you didn't order a new meter i picked up one of these and it's awesome http://www.harborfreight.com/5-in-1-digital-multimeter-98674.html
includes a temperature probe very useful.
On topic I wouldn't muck about with psu's that are too old and i would avoid dell psu's of that age period they're known for being wired in a non standard maner