I've just fitted a secondhand MkIV sat nav module to replace my broken MkIII. I put it in and turned it on, all seemed fine on the monitor but when I selected navigation a message came up insert CD/DVD even though I had already put one in. I changed the CD to a different one I had and that didn't work either. I left it a while and then a message came up saying "error reading disk"


The unit seems to take the disk ok, it spins up and it ejects ok, just can't read them.

Any suggestions?