Here' s the thing. I currenty have XP 32-bit and plan to build a new pc, keeping my current hard drives so I decided to get the upgrade version of windows 7 to upgrade my XP 32-bit to win 7 64-bit through a clean install. I have 3 drives: C (free:7,08 gigs/overall:25,5), D (free:10,8/overall:11,7) and F (free:423/overall:465) in which C is the primary where system info is stored (probably the OS as well). C and D are included in the same HDD of 40 gigs capacity which was splitted into two (C and D). The 2nd HDD (F) I bought it some months ago as the original wasn' t enough. So my main question is: if the 64-bit win 7 require 20 gigs of space does it mean that I don' t have enough space in C(where I was planning to install it) or that from the 25,5 gigs of C the 20 will be given to windows 7 OS and the other 5,5 will remain for the Windows.old folder and other stuff? Sorry for the long post-I tried to be as clear as possible.