MIL Light and scantool problem

[trawdener]

I have a 2001 model SLK200K. The MIL light has come on. It did this the other week and it was an O2 sensor when the garage checked. I bought an ELM320 interface and hooked it up to my laptop using EasyOBDII 2005 version 2.1. Unfortunately it isn't talking to the car. There is a light on the interface which is on, so it is getting power. I have seen two varieties of these interfaces, one being a standard one and one being "Can bus". I think I have the standard one. Can anyone help please. I only want to turn the light off!!!
Thanks
Geoff aka
Frustrated of Trawden
geoff.trawden@tiscali.co.uk