XP Pro fully updated on all four machines. This home network has worked for several years without problems. All sharing, workgroup name, etc are correctly set up. Suddenly, one machine will not let others connect although each one has a user account on it. It keeps putting up a login box but only offers 'Guest' as the possible login. Even so, it still won't allow a Guest login but just keeps throwing up the login box with no error messages or explanation. I've run through everything in the network troubleshooter to no avail. The rogue machine can connect to the other three and transfer files without problem! Help please?

On the machine that can't be accessed, open a command prompt window and type this command: net user guest /active:yesBoulder Computer Maven Microsoft Most Valuable Professional