What I'm trying to do is use my LM52's lifetime maps feature to download maps for other Garmin devices that do NOT have lifetime maps (many of which are older and don't have the same features like the LM52 like junction view, and perhaps for some devices that have more features but no LM tag). I also want to make sure I download all of the correct and appropriate "accessory" files like the junction view files, etc... as applicable to the device I am trying to update maps on.

What's the steps again?

I think it goes something like this:

1. Copy GarminDevice.xml from the Garmin I want to update to a USB stick.
2. Change that GarminDevice.xml file on the USB stick with the RegistrationCode key from the LM device's GarminDevice.xml.
3. Run Express on the USB stick.
4. Copy downloaded files to the Garmin GPS device I want to update.
5. Run Protected Garmin file toolkit_2254_x64.exe on the big map file (gmapprom).

Is that kind of the way it works or did I skip a step? I think there was also a step where I need to unlock the map using a Garmin decrypter/unlocker, but I don't remember if it applies to this procedure.

Side-note: Also, I seem to be having trouble attaching old Garmin units to my PC after upgrading from 7->10. It starts out like it's going into PC mode (with the progress bar and everything), but then just goes into navigation. This happened to a NUVI 200 and 275. The LM52 did manage to connect, though.

Using the same USB cable and the same devices, I was able to connect to one laptop with Win10 and one laptop with Linux, so it's neither the Garmin device's nor the USB cable's problem.

There is no need to create a clone device,both the nuvi 200 & 275 (most proberly 265) use only the gmapprom.img which you have on the nuvi 52.Make a copy on to your PC & unlock with gimgun.
You will most proberly need to use a FAT 32 formatted SD card <32Gb as the latest maps for N. America are larger than the internal storage.
Change the name from gmapprom.img to gmapsupp.img & copy it into a folder you will have to create called Garmin.
You will not need to connect the nuvi 2xx devices,only the SD card to your PC,but try another USB cable

I got around the large file name issue by using a dummy file. Basically I used Dummy File Creator to fill up a flash drive so that only a gig or two remained and when I did the map update, Express recognized my limited space and let me select a reduced map (NE, NW, SE, etc... of USA). The maps you can select overlap so even if you live in the middle of the USA, you should still be fine. I picked the one I needed, unlocked it, and copied it as GMAPPROM directly to the device, overwriting the existing map. This removes the SD card requirement, reducing the total cost of the device.

I also used a laptop to copy the files to the device. I guess it's an issue with my drivers, because it used to work. Something must have happened to the drivers when I updated to Win10, because other Win10 and Linux machines work just fine with the same cable and the same devices.

I also copied whatever other files were downloaded to the flash drive. Probably not being used, but whatever.

Now I'm trying to get POIs for it so I can search for businesses/gas stations/etc... Any idea where to get these?

Points of interests you mention are part of the map,additional FourSquare maps are NOT compatable with your nuvi 2xx's

I see, so the GPI files that are kept separately are only for more recent Garmin units?

Any way to "browse" the points of interest on a GMAPPROM img file on a PC to check if something is there?

vassock wrote:I see, so the GPI files that are kept separately are only for more recent Garmin units?

Any way to "browse" the points of interest on a GMAPPROM img file on a PC to check if something is there?

Just Install Mapsource & use GE with your nuvi 52 to install the maps to your PC,then you can Find POI's by catagory.