Perhaps returning the system to a date before you attempted the change will cure it.
System Restore is a feature of Windows XP that allows you to restore your computer to a previous known working state in the event of a problem. This is done without loss of personal files or data such as word processing documents, spreadsheets, music, images, etc. This feature is enabled by default and runs in the background making backups after certain events happen on your computer. System restore functions are only available to an administrator of the computer, therefore if you are not an administrator, you will not be able to follow this tutorial.
Windows XP System Restore Guidehttp://www.bleepingcomputer.com/tutorials/windows-xp-system-restore-guide/