If you are planning to run a 64bit edition of Windows that is the full featured version of Vista seen there. For price saving and the lack of 4 items 3 for networking and one intended as a hardware protection type the next down is the Home Premium for about $110 for the 32bit version.
The 64bit editions of Vista are still much like what was seen with XP Pro 664bit as far as driver support while the new Windows is finally seeing something there. All the games and software still coming out however are primarily 32bit.
Besides being a newer version of Windows needing updated versions of programs not everything will run due to the structure. That was seen when going from the 16bit 95 to the newer 32bit 98 with full 32bit support there.
