The Explorer can be disabled by preventing the system from running it.
Rename the following value:
[HKLM\init] Launch50=_explorer.exe
Don't forget to save the Registry.
ActiveSync will still work on CE 5 and CE 6, so you can access your module using ActiveSync. Windows Embedded Compact 7 needs the explorer enabled if you want to use ActiveSync (Mobile Device Center).
To re-enable the explorer, follow the steps mentioned below. An empty storage medium like USB stick or SD card is required.
21#\windows\explorer.exe
[HKLM\init] Launch50=explorer.exe