Windows automatically does that unless you delete/reformat the partition before reinstallation. It's safe to delete, and while any malware would be present in that folder it shouldn't pose a threat unless launched, so I would delete it soon.
I just reinstalled vista because it kept freezing (either b/c of a software issue or spyware) but i see that i still have everything from my computer - under "windows.old" - should i delete it? I already backed up what i wanted and if i had spyware can it still be there and now it will spread (also it takes up a lot of my memory).
Any one know what this is about? (I thought that after i reinstalled windows that everything would be gone)