Windows XP Instructions
1. Click on the 'Start' button and select 'Control Panel.' Double click on 'Performance and Maintenance,' then on 'System,' and click the 'System Restore' tab.
2. Click on the entry labeled 'Restore my computer to an earlier time' on the 'Welcome to System Restore' window and select 'Next.'

3. Choose a date on the list of restore points before the registry error began on the 'Select a Restore Point' page. This list is labeled 'On this list, click a restore point.' Select 'Next.' Select 'Next' again on the confirmation screen. Click the 'OK' button after to confirm the the changes.
Windows Vista Instructions
4. Click on the 'Start' button, then click on the box labeled 'Start Search' and type 'systempropertiesprotection.'
5. Select the tab labeled 'System Protection' and select 'System Restore.'
6. Click on the entry labeled 'Choose a different Restore Point' and select 'Next.' Choose a date for the restore point before the registry error began. Select 'Next.' Select 'Next' once more in the confirmation window.
7. Click 'OK' to confirm the changes made.
Windows 7 Instructions
8. Click on the 'Start' button and type 'System Restore' in the search box. Select 'System Restore' in the list of results.
9. Click on the entry labeled 'Choose a different Restore Point' and select 'Next.' Choose a date for the restore point before the registry error began. Select 'Next.' Select 'Next' once more in the confirmation window.
10. Click the 'OK' button to confirm the the changes.