Give Mercedes-Benz credit for putting a PC Card slot in the dash of many models. That lets you copy MP3 or WMA music from your PC to a cheap SD or Compact Flash (CF) card, plug it into a cheap PC Card adapter, then plug it into the dash of your not-so-cheap Benz. The adapter (also called a PCMCIA adatper) and a 2GB SD card each cost about $10, although you can pay more. But check out the prices if you order one of each from an authorized Mercedes-Benz dealer: $102 for the PCMCIA multi-card reader, $48 for a 2GB Mercedes-Benz logo'd SD Card.