“Tell me what do” is thanks to the short space you get to put a title.
My machine is a quad core 2.4ghz pentium, 4gb of ram, geforce 8800 ultra, sound blaster xfi gamer.
just under a terrabyte of HD space, of which over 200gb is now devoted to XP.
Other than try out the software/games that wouldn’t work on vista what shall I do to take advantage/play with my new multi-OS computer setup.
What would you do? (Or what have you done in this situation)
I hate you.
But seriously, MOST stuff should work fine in Vista. I’d actually recommend format/reinstall of Vista too, just to get rid of all the pre-bundled software and crap they usually install (unless you built the rig yourself, in which case, you rule).
Didn’t build the rig myself, but I did re-install vista very soon after i got it. I needed to to set up raid 0
I’d use XP for all my non-DX10 gaming, given Vista’s poor gaming performance compared to XP. The 8800 Ultra is a nice card; it’s a shame to see it wasted in Vista. 
Part of my reason for deciding to dual boot was so I could play my older splinter cell games, having completed Doulbe Agent.