> Anyway, I'm looking for an unofficial build of mame that will let me get the
> oomph out of my PC without utterly taxing it.

It doesn't exist.

I'm not looking to play anything
> post-'00

Then you should be fine with your current PC.

A 3GHz P4 is more than fast enough to run the vast majority of games supported by mame at full speed. My guess is you have some kind of configuration issue.

Which games are giving you problems?

-Sune