I had this problem for ages and tried lots of things.
If you have more than 1 user account then this may be the problem. The only thing that worked in the end was deleting the user accounts so you just have one main one to work from. XP will save any files that are personal to the the user account, you delete, and stick a shortcut on to your desktop and name it whatever the user account was called.
Once you have deleted the user accounts you then need to disable the password for the one you have left.
This worked for me, I saw it on a forum somewhere else.
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