Just don't expect to see any features found on the current line up of nüvis by upgrading the firmware. Except for spoken street names, which appeared on the 260W, none of the features people seem to ask for most (lane assist, junction view, and the speed limit indicator) appeared on any of these units.

For a 2007 vintage 250W, the last firmware revision was 4.00. But, use webupdater to do the update. That is far easier, plus you can replace anything missing such as voices, if you need to.