Question : Problem: Intel D875PBZ motherboard will not start when an ATI All in wonder AGP card, or an ATI TV Wonder PCI card is installed, but works flawlessly with straight AGP card.

I had a power supply die on this PC with an Intel D875PBZ motherboard. Replaced the PSU with a higher rated model.
It had an ATI AIW 8500DV installed at the time but wouldn't startup after replacing the PSU. Suspecting the video card, I replaced it with an AGP video card and it worked flawlessly.
Thinking I had a bad video card due to some power surge, I  installed the AIW 8500DV AGP-4x card on 2 other PC's to ensure it was the problem,and lo and behold it worked flawlessly with no ill effects.
Now I try a  PCI slot TV Tuner card (ATI theater 550 pro) and the same symptoms occur. I've also installed an ATI AIW 9600XT AGP-8x with the same results. Both cards are tested and working in other PC's
This is a weird one. I install either an AIW AGP card  or a PCI TV tuner card with a working AGP card and the PC won't start.
I am thinking that this is a chipset level problem on the motherboard, that occurred when the PSU cooked, but it only effects cards with tv inputs. Anyone ever come accross this type of problem?
How does the tv tuner card or tv tuner section of an AIW card converse with the chipset, and how does it differ from an ordinary AGP video card.

Answer : Problem: Intel D875PBZ motherboard will not start when an ATI All in wonder AGP card, or an ATI TV Wonder PCI card is installed, but works flawlessly with straight AGP card.

Both your 1.5v and 3.3v lines are very low (clearly out of spec).   While that COULD be a sensor issue;  it could also mean you've found the culprit => your new PSU !!  (or, of course, something that's failed on the motherboard and dragging these lines low -- but I'd suspect the PSU first)

Do you have another PSU you can try?

Just FYI, my 1.5v line reads 1.447; my 3.3v line reads 3.256
ATX spec for the 3.3v supply is 5% => so anything below 3.14v is out-of-spec => you might want to measure your 3.3v line with a multimeter, just to confirm it's not just a sensor issue.

Not sure why a low 3.3v line would have the impact you're seeing (still seems strange) ... but with such a significantly out-of-spec voltage (15% low is 3x the spec's tolerance), I'd certainly resolve that before anything else.