i have vista 64 on my laptop and it runs great. the only problems are that most applications that require driver usage such as clockgen, require special treatment. i have to start my computer hit f8 and tell it to turn off driver signing enforcement (built in feature to x64, kinda sux in my opinion) however in performance, the os will make use of the 64bit bus width in the processor, but in ur common apps, they generally only use 32bit unless it is specifically a 64bit app. So yes it has its ups and downs. also remember that 16 bit programs will not run AT ALL. support for it has been dropped. last up is that 32 bit = 3.5 gb ram and 64 bit = as much as you can put in it right now lol i think its actually in the terrabyte region