updater.exe is not webupdater.
The other way to convert your unit without updater.exe is to use RGN_Tool to save your rgn file to a gupdate.gcd file ., remember to override swv to same number both boot and fw_all.
and not forget to delete a gupdate.gcd within .system in your unit.
Place gupdate.gcd in sd card\garmin\gupdate.gcd
turn off unit --> insert card--> turn on unit --> begin flashing.
But I advice you should have updater.exe because you need this tool for recover nuvi if you get in problem ie rebooting.