Logon failure: Unknown user or bad password

While looking for clues on the Win2k system I realized that the date was wrong (I had set it forward ten days as part of the tests that I had been doing). I set it back to the correct date AND ALL PROBLEMS DISAPPEARED. Win7 prompted me for a username/password which I entered and which was immediately accepted, and I had full access again

 http://windows7forums.com/windows-7-support/16942-logon-failure-unknown-user-bad-password-*solved-*.html