The size of XP on disk will be much larger than 1gig and it grows daily with system restore. You can limit how much system restore will occupy by changing the slider in it's settings. This eliminates some possible restore points. I test alot of programs, some of which play havoc with the registry, and I gotten away with 500mb dedicated to the restore cache. Another thing to watch for is, if you do a reinstall of the os without a reformat files remain from your programs. I discovered this after I reinstalled. All the programs appeared erased in the program file folder. The drive before 15gig 55% full, after 15gig 78% full. I found the files in protected folders and couldn't figure how to restore them, so I reformatted. Perhaps this is a NTFS file protection, I don't know yet.