I believe the original bootstrap.sh checks if the files to be backed up exist and are not symbolic links. In case of XP I think that not backing up if "..\.spf13-vim-3" exists would probably be sufficient to save updating users the wait. If they decided to use the distribution the .vimrc should not be edited manually anyway.
Since there is no mklink in windows XP and installing the tool that provides this function is only possible on NTFS filesystems I created this installer for my colleagues at work. Probably far from a perfect solution but just so people on old XP boxes can enjoy the awesomness easily.