If CNNAM is not in Mapsetoolkit list, something is wrong-
Do you have the CNNAM folder in
(in XP - C:\Documents and Settings\All Users\Application Data\GARMIN\Maps) or
(in Vista, Windows 7 - C:\Users\username\AppData\Roaming\Garmin\Maps)?
Which mapsource version do you have ?
In old Mapsource versions you have to install it in the registry too.
In this case is better to update Mapsource, if you want a previous version too, you can have both working in your pc-

Before you install the new one,make a copy of the mapsource.exe file (old one) and put it aside. Install the new one. When the install is complete copy the old mapsource.exe (renamed of course) mapsource_old.exe for example to your mapsource folder. Note you only need the mapsource EXE. .
The last step is to create a shortcut to the old mapsource executable-