I've never really heard of a p3 and by looking at Newegg's power supply screen (
CLICK ME!), I cant see anything, so I would assume the P3 means that it is Pentium 3 ready, which would also make sense if the 2001 in the middle, meant it was made/designed in 2001.
I dont know much about micro ATX comps at all, but I would assume that a MicroATX Powersupply would do the job. I think a standard ATX powersupply might be too big.
Before I would make any desicions I would check out tomshardware.com first. Just search for MicroATX powersupplies and see what comes up.

AKA Shinobi
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