Ok, i just got vista x64, i already have x64 windows (old version) on my new build, i was wondering if i can put in the x64 vista and intall it and erase the old OS?? How does it work without using up more space, also when i finished getting the OS intalled i went in to see how much space i had and it said i had 291 GB out of 320GB and the only thing i installed was the OS, it was 680mb, but it was in a zipped folder..know what i mean?? Thanks for any help.