Here is an answer to what Nav unit you have...it should be MKIV, also updating the OS is on here as well, downloading the image and writing to a CD is not on that how to, search this forum:
http://www.x3world.com/articles/all-...ystem-faq.html
It also looks like (from Navteq) BMW - North America Map DVD - High Version 2009.1 is the latest version. See link (don't know if it will work)
http://www.navigation.com/is-bin/INT...llProducts=YES