Well, I tried 64 bit OS once, both windows and Linux. This was just a few months ago, and most of the hardware manufacturers didn't support 64 bit (windows or Linux). Whilst ATI had 64bit linux graphics drivers, they didn't work right with my x1650 card, X would crash when I played a video
The outcome was I went back to 32 bit linux...
Anyway, enough of my pity story, I'd suggest 32 bit linux, or waiting for ndis to support vista drivers. Your choice