May also depend on whether you install the 32-bit Vista or the 64-bit (both are supposed to be on the DVD).  XP 64-bit has had problems primarily with the installer DAZ used which required it to be run in a restricted 32 bit environment (Win98 compatibility mode) through installation and first start until you had your serial number registered.

Since that stage I haven't had any noticeable problems running B6 on XP 64 bit though it won't recognize any extra memory the OS may have available.

Brett