When you double-click a folder, or single-click if you are configured that way, the Windows XP Search Companion may start?

NOTE: If you configured settings for other actions, such as Open Command Window Here or Print Directory Listing, one of these actions may start instead of Search Companion.

This problem can be caused by Explorer.exe blanking a string value in the registry during one of your configuration sessions.

To resolve the issue, copy / paste the following to a <Folder_Path>\none.reg file and then running regedit /s <Folder_Path>\none.reg:

REGEDIT4

\[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Directory\shell\]
@="none"