Thanks for the tips but it's worth noting that if anyone has any other Garmin stuff installed in addition to Mobile PC they will put themselves in a world of hurt if they follow those instructions.
If someone has Mapsource and/or Basecamp and one or more of Garmin's map products installed, your instructions will wipe out all of that, so they will all have to be reinstalled, too. That's a bunch of work and takes a long time.
Best to just use the Control Panel to uninstall Mobile PC and then run a good registry cleaner so that all stuff related to only Mobile PC is cleaned out. I use the registry cleaner in Advanced SystemCare (freeware version)
for that sort of thing. There are others.
As a general rule, manual editing of the registry isn't really wise unless you know how to make backups of the registry files (not easily done), are very familiar with the registry and generally pretty technically competent. And have pretty good nerves.