For those running across this thread in a search for 'dongle not recognized' troubleshooting information, be aware that the Service Center for Legacy CD is no longer being sold. The new version of PC Service Center (v7) includes a parallel-port dongle that should address the problems in the USB MUD.
I may add, parenthetically, that I am very glad of this, as approximately 1 out of 4 computers I have run PC Service Center 6 on have had dongle-recognition problems. In fact, in spite of its usefulness, I had pretty well decided against buying any further versions of PC Service Center until this dongle problem had been addressed.