i run xp64 on my rendering machine as part of a dual-boot configuration.  it works great,  a bit of a challenge but well worth it.  also, a word to the wise, spend a few bucks and install it on a large separate hard drive.  i also installed 4 gigs of dual channel memory and poser seven runs like a dream..  follow the links from 'planet 64' for instructions on a multi boot installation.  carrara plays very well in this environment as well.