If you are familiar with RegClean, the Classes Vac will do about the same thing.  It will find bad keys in the Classes section of the Registry and remove them.

To use the Classes Vac, you must first click on the Find Bad Entries button.  A flashlight will appear in the upper right hand corner and the Classes Vac will begin to find bad keys and list them in the listbox.  When the flashlight disappears, the search is finished.  Up to this point, nothing has been removed from the Registry.

You can use the buttons below the listbox to check all and uncheck all items (Check All or Uncheck All), to print out the list (Print List), or to open up RegEdit and show where the selected key is in the Registry (Show Key).

To remove a bad key in the list from the Registry, click on the Clean Checked Items Above button.  The entries will be removed from the Registry and put in Undo.

The "Find and Delete Bad Entries as part of Automated Scans" checkbox lets you include the Classes Vac in the automated scans.