I use win7 64 bit version. file transfer/copy, start up, running/openning apps at the the same time and video encoding is faster than xp(or vista32bit and win7 32bit) even with my old desktop with only 2gig of ram.
and oh Photoshop 64bit rocks!
and note: you need to turn off the windows search(indexing option), or the system will crawl. lol