These tracks are now available again for download. Many thanks to fellow ADVer deputyjones who offered some server space.
Go to http://dsam-mi.org/GPS_Files/
and you will see a directory of folders that contain the files. You should be able to choose the proper directory without much trouble. The individual files will have names that are the same as or similar to the file names listed when the files were hosted on ADV.
The files are listed as .zip files. If you left click/open the file, you will open it in your computer's temporary internet directory. Depending on how you have your computer set up, clicking on the .gpx will open the file with Mapsource so you can look at it. Remember, it is in your temporary internet files.
To save the file in one of your neatly filed directories, "left click/save" or "right click/save target as" and put it where you want to keep it.
Some of the files have an associated spreadsheet file with points of interest (Black Hills, Pony Express, etc). Same procedures apply.
Happy to have quick and easy access to these files again.