There are 2 settings on the GPS for USB connection: "MS ACTIVESYNC" or "MASS STORAGE". With MASS STORAGE selected (default I think), when plugged in to my Win8 laptop Windows Explorer opens one "Removable Disk", which points to "ResidentFlash".
When MS ACTIVESYNC is selected, my laptop downloaded and installed Windows Mobile. Using File Management from there I see 3 folders: "\", "Network" and "ResidentFlash". The "\" folder is the WinCE install location; formatted TFAT and REPORTED by Windoz as less than 500K in size (43MB of files), "Network" is a 0 byte sized folder with no contents shown, and "ResidentFlash" is FAT32, where PRIMO in installed.
Looks like with the addition of a few WinCE tools, it should be easy to HACK the Windows side of it, but as already stated, easy to turn it into a brick too!
I haven't had any success with adding a SKIN, as it seems that the ones I have found do not support 800x480 resolution. I believe I read that there are ways around that.
I would like to work on a custom skin, kind of like BLRFL had for the Lowrance (I miss my Lowrance!) There are thing on the default screen that I don't really care for. I don't want the house numbers at the top, would rather have a compass. Would like to have a clock and current speed when running a route, yadda, yadda. And the routing "Skip to next waypoint" would be nice too.
So I'll putz around with this and see what I can figure out. Already joined GPSPassion, Motor-Forum, GPS Power and NaviTotal looking for ways to tinker with it!