If you have installed both Google Deskbar and Google Desktop and you want to search your desktop from the deskbar, there's an easy way.

1. Go to Registry (Windows-R, type regedit).
2. Navigate to HKEY_CURRENT_USER\Software\Google\ Google Desktop\API\search_url
3. Copy the value from search_url key
4. Go to Google Deskbar options
5. Add a new search in "Customized Searches". At the URL field, enter the value from step 3 and add {1} at the end. The final URL should look like: http://localhost:4664/search&s={security_code}?q=
6. Right-click on Google Desktop tray icon and select "None", instead of Sidebar, Deskbar or Floating Deskbar.