I just made a copy of my vista home premium x86 and it takes 6GB of space on the HDD. About how much memory it's using is all depending on how much you have in your system and what applications you use as there is superfetch in vista that loads the most common apps you usualy run, so you can't just ask anyone how much memory it will take as it is all depending on the user and what you use. Usualy vista tries to use the most amount of memory, and this is a good thing as you don't want memory to be unused. But for example i have 3GB atm, my vista takes 1GB atm, in a couple of days it'll most pro