I was able to download Maptech Viewer at the link below

http://www.maptechnavigation.com/support/downloads.cfm?CFID=2461853&CFTO...

Then I downloaded charts from NOAA, copied them into the source file for the Chart Navigator allowing navigation on my computer.
This link is; http://www.charts.noaa.gov/RNCs/RNCs.shtml

Note these charts do not include Clinton Lake or other small lakes, but does cover the Great Lakes well. I found it very useful on our Door County trip.

Hope you can find this useful.

Commodore
Joe Budden