Fozzie, I had the same problem a couple of years ago when I bought a used Nav2 off ebay without software.
I spoke to Garmin customer support twice. The first guy was a prick who didn't want to know, and told me they don't support online auction items. The second guy was called mark timms and was a gent. He agreed it isn't their ususal policy to support online auction kit. He then re-registered my unit in my name and sent me copies of City Navigator Europe by post, and my unlock code via email.
You could phone Garmin as I did and get their help.
The problem you will then have is that you can't install the map data from CD as you need to initiate the install using a BMW Nav2 installer CD. If you need one of these, give me a PM and I can burn you a copy of the BM installer CD for the Nav 2 software.
Don't go buying new Garmin mapping from ebay without first checking it has the unlock certificate. Better still, try to get them free from Garmin customer support.