How to Restore a Class Not Registered Error
When you try to open the Windows Explorer program on your computer, you may receive an error message that reads, "Class not registered." The cause of the error is most likely the ExplorerFrame.dll file needing to be re-registered. If re-registering the file does not stop the Explorer error then the file may be fully corrupted. Your last option to fix the error is to restore your computer to a point before the error began to occur.
Right-click on the "Start" button from your desktop and click the "Explore" option from the shortcut menu.
Click the "OK" button that appears for the "Class Not Registered" error to close out of the dialog box.
Click the "Start" button from the desktop and then click the "Run" button. If you don't see the "Run" button, type "Run" in the search field and press "Enter."
Enter "regsvr32 ExplorerFrame.dll" into the "Open" field. Click the "OK" button and then try to run Windows Explorer again. Click the "Start" button from your desktop if you still receive the error and then click the "All Programs" option.
Select the "Accessories" option and then click the "System Tools" option. Click the "System Restore" option.
Click the "Restore my computer to an earlier time" option and then select a restore date for a time before the error occurred. Click the "Restore" button and your computer will automatically restart.