Ken,
I would recommend that you do something else as well, to save those maps you no longer have the CD for. First, back them up on something .. thumb drive, optical media, whatever.
For those who don't know, all the Garmin map data files are in the \Garmin folder which is normally in the root directory on your C: drive, unless you've figured out some way to force it somewhere else. For any map product you need the folder with the relevant product name and any sub-folders, plus anything in the \Garmin folder that looks even remotely like it belongs to that product. You can tell by the file names.
Then go into the registry and copy the registry entries related to the product so you can enter them manually if you ever have to restore the map files from the backup.
You can see the MapSource registry entries here:
HKEY_LOCAL_MACHINE\SOFTWARE\Garmin\MapSource\Families
Click on the plus signs beside Families and each of the keys under Families to see what's there. Click on the keys themselves to see what keys and values they contain (they'll show up in the right-hand pane when you click on the key). Write it all down or take a screen shot (PrtScn or Alt-PrtScn) and save it somewhere.
If you have a backup copy of the map files in C:\Garmin and the relevant sub-directories you can completely restore them to MapSource by simply adding the necessary entries manually into the Registry. I have done it on occasion. (I mess with my machines a lot, so I'm in the habit of making lots of backups!)
For the uninitiated, those registry keys simply tell MapSource the name of the product and where to find its image files. If you take a look at them, you'll see there's no magic to it at all.
...ken...