When you work with custom forms, you can eventually have a long list of folder names on the Look in list in the Choose Form dialog. You can clear this list by editing the registry.
- In the Start menu's Search field or in the Run command (Windows key + R to open Run), type regedit to open the registry editor.
- Browse to the Office Explorer key then delete the Namespaces value.
- Restart Outlook for the change to take effect.
- Outlook will recreate an empty key, with only the default folders listed.
For Outlook 2010, the key is at:
HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Office Explorer Value: Namespaces
For a list of other MRU lists you can clear from the registry (and ready-to-run registry files for many of the values), see Clearing Outlook's Most Recently Used (MRU) lists (Slipstick.com)
Published February 9, 2012. Last updated on August 7, 2015.