Snap!
Probably something to do with this.
Access authorization, registration, provision
Snap-on grants an access authorization for access to the Technical Information on the following conditions:
2.1 The User belongs to the authorized category of persons under the Block Exemption Regulation (GVO no. 1400/2002 of 31 July 2002) with their registered office within the European Union or the European Economic Area:
* Independent workshop
* Manufacturer of repair equipment
* Independent parts dealer
* Publisher of technical information
* Automotive club employee
* Breakdown assistance employee
* Provider of inspection and testing services
* Employee of a basic and further training facility for motor vehicle mechanics
Please notice its Snap-on tools who are refusing you access NOT the manufacturer Mercedes Benz. Those corporate lawyer dudes certainly earn their money.
On another note a poster on "another forum" has indicated that if you are one of those low lifes that has an illegal copy of the WIS or EPC on disc
DO NOT UPGRADE TO WINDOWS VISTA cos you will have great difficulty in making them work ! Thats according to him and I could never condone such practices anyway.