It doesn't look like there's an easy, built-in way to mess with file permissions and file ownership under Windows XP Home. Apparently you're just supposed to click the "Security" tab in the File Properties dialog but I see no such thing and the tips to enable this tab are for XP Pro. How to get around this?

Cygwin to the rescue! From the bash prompt, chown and chmod work as expected. For example, to change a file's owner from user brian to user Administrator, simply use chown Administrator file. To change the owner and group on a whole directory tree: chown -R Administrator.SYSTEM *. See man pages for chown and chmod for other uses.