Finally got it working this weekend - turns out it was just a license issue. So now I've got v3.9.2 up and running, no OS changes required.
Man, it's great - loads up in about 5 seconds, compared to Maya 3 which takes about a minute. It also uses only 14mb ram at startup, whereas Maya 3 uses close to 60mb. I do miss the days before OOP/Java/crap bloatware.
As far as the old interface goes, I like it. It doesn't call attention to itself - lets you focus on the viewports. Seems like XSI's was over-compensation for 3D's "archaic" look, hence the fancy rounded buttons with beveled edges and shading. Overkill.
I like text buttons - you can immediately read their function. Soft|3D, Lightwave, and just a few other packages had that advantage. A far cry from 3dsmax, which is basically layers upon layers of cryptic icons.
Anyway, time to go render some dinosaurs...
Awesome. I hope your dinos have feathers!
(Man, it would be nice if I could get Maya to dump all the icons in favor of text.)