try the following: get cmagic4, open it and load the .dat file of the track you want to move to another slot. Click on "Edit Gp4 Info". In the pop up you should see an entry called "prefix" which will most likely have the value "suzuka2001". click on the box containing the value to select/highlight it and press "delete" at the bottom of the window. Save, close cmagic and try again in gp4. This might do the trick. This happens when the author links the .wad to the .dat to bypass the standard gp4 assignment of dat to wad.
used to be GPGSL's Nick Heidfeld