Your Euro specification COMAND may differ from U.S. spec; but my '00 S500 had a built-in CD slot that was for the nav disc only; my owner's manual cautioned against inserting music CDs, saying they may fail to eject and could damage the reader.
Some later COMAND units exported to the U.S. did have a single slot music CD player/nav disc reader.
__________________
2005 S500 4-Matic
with Gateway 500 iPod integration
Formerly: 2000 S500
with Ice>Link iPod integration
Moto V710 phone with MikBox
Upgraded Voice Control
Vehicle: Mercedes S500L W220 Gilera Runner 180sp BMW 323i SE E46 Suzuki GSX-R 600 K4
Location: London
Posts: 97
Well I put an audio CD in there since my cd changer is not working but it still said the same thing-no cd changer. When I pressed the nav button, it said insert nav cd