Hi Jon,
You always need a GPS receiver to receive the satellite signals.
The little Garmin (and TomTom and Magellan, etc.) devices that you see mounted on people's dashboards have GPS receivers built right into them.
The only reason Garmin sells a version of Mobile PC without a GPS receiver is that some people already own GPS receivers and only need the navigation software and maps.
For your purposes, the software-only version of Mobile PC is not an option for two reasons. One is that it sounds like you do not have a GPS receiver. The other is that you cannot add most other Garmin maps to it. You may have read about "locked" maps and Garmin "unlock codes" and such. Well, they require a Garmin GPS receiver serial number in order to work.
So, if you want to use Garmin maps and Garmin Mobile PC you need one of the deluxe versions with either the GPS20x USB receiver or the GPS10x Bluetooth receiver.
With either of those deluxe packages you will be able to easily buy and add other Garmin maps, whether they are locked or not.
If you want to see what the coverage for Mobile PC Europe is, check their online map viewer for the City Navigator Europe maps (that's what comes bundled with Mobile PC Europe).
Click on the following link. Click on the map product you want to look at. Click on the "View Map" tab. This will show you an overview of the coverage. On the map coverage picture there will be a link you can click to view the details. It's interactive so you can zoom and pan to check areas of high interest.
City Navigator NT
You can check out City Navigator Europe and City Navigator Russia to see if they will give you coverage that is useful.
Mobile PC (all versions) comes with an excellent world map built into it. If there is an area that you would like to see as an example post it here and we'll pop up a screenshot or two for you.
Any custom POI files that can be loaded onto a Garmin handheld can be loaded into Mobile PC.
In order to understand what Mobile PC really is, just imagine that you can take the software out of a Garmin Nuvi and stuff it into your computer and then it uses your computer display to display everything and it needs an external GPS receiver to get its satellite signals. The commands and features are very similar to the commands and features on a Nuvi. If you have a touchscreen you can even program it like a Nuvi by touching the screen.
I hope I didn't miss anything.
...ken...