>I have about a dozen customers that say they can not install MS SQL 2005 Express on their XP computers. The install fails.
>A couple of them I have been able to help by asking them to run Windows update and that took care of it, but I have quite a few that are up to date on Windows updates and still can't install MS SQL Express 2005.
>

What error do they get? See if http://yukonspace.blogspot.com/2007/09/troubleshooting-sql-server-setup-and.html helps.