I should also point out ... if windows.old contains a previous installation
of Windows Vista, things are a lot trickier due to any application
compatability junctions that may be in there.

If you look at the permissions on these junctions (such as All Users inside
the users folder), they have an entry on them that denies everyone access to
them. DO NOT remove this deny permission and perform the steps listed in my
previous post, or you may end up corrupting your current installation of
Vista.

The correct way to delete junctions is with the fsutil command-line tool:

fsutil reparsepoint delete <filename>

In any case, letting the cleanup wizard take care of things in this scenario
is much easier

- JB