Yes you can. It's detailed in the MPC 4000 Reference guide on page 206.
1. Hit "Program" and verify that you are in the "LIST" page.
2. Move the cursor to the Program field and select "Window"
3. Select "Convert' F3 softkey
4. In Program source, select the program that you want to convert.
5. Give it a new name in the new name field
6. In covert field select Keygroup --> Drum
7. Select F6 softkey "Do It'
Whala now you have a drum program.
Cheers,
Dave