How can I clear the Google Toolbar search history in the registry?

Start a registry editor (e.g., regedit.exe).

Navigate to the HKEY_CURRENT_USERSoftwareGoogleNavClient1.1 registry subkey (yes, the registry subkey is 1.1, even though you might have installed version 2.0 of the toolbar).

Select the History subkey, click the Del key on your keyboard, then click Yes to the confirmation.

Close the registry editor.