So I have Windows XP Pro, and everytime I reboot my computer and start up, it tells me the password for my created Admin-level user is invalid.

I then have to ctrl-alt-delete to get to the dialog box and for a username type "Administrator" and the Administrator password, go to Start->Control Panel->Computer Management->Local Users and Groups->Users and then right-click on my user, choose "Properties" and the "Account is locked out" checkbox is checked. I uncheck it, switch user, and then my password will let me into my Admin-level user account until I reboot my computer and I have to do it all over again.

Any ideas on what would cause my account to be "locked out" every time I turn my computer off and back on?

One day this just started and has never stopped.

Sounds like you need to remove a virus or malware. Just because you have a good virus detector and you scan your PC every day does not mean that your PC is clean. If you are running one of these anti-virus programs, use the other to do the check. Even if your PC is clean, it can not hurt to check and rule out that problem. Go to:-
Download and run to remove any viruses you may have. (Sometimes a virus will stop you accessing an anti-virus site, so try going through safe mode (Tap F8 on boot up) and see if you can access it there.)
If you can not access either site in safe mode, you can make a DOS CD with another PC from either of these sites and boot your PC with it and scan from DOS.

Then go to :-
Download, malwarebytes, then run a “quick check” your PC for any problems, if still there, do a “full scan.”

If that has not helped, then maybe a Windows repair is required. If you want to repair your installation with your OS disk, go to:-

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