If this is a WinCE headunit and the GPS app is on an SD card, you can always access the internal files by replacing the normal navigation app .exe file with a WinCE file explorer. Then, instead of the navi app starting, a file explorer will start where you can access the internal files (and can get into Control Panel or even the WinCE desktop itself).

Search for Total Commander for WinCE for a good WinCE file explorer.

Thanks for the tip. Once I do get a command prompt what are my next steps? My goal is to return to the wonky way the system worked (but it did work) when out of the box. Apparently you can't get there with SYS.TXT unless you made a full backup of the original SD card, which of course I didn't do. I do own Acronis TruImage, however, if I could figure out where to get a replacement card from the "factory"

I don't see an .EXE in TotalCommander, just a bunch of CABs?