I have tried using C-Map and thought it was useless, running XP service pack 3. Worse still under Vista. PC Planner (Navionics) crashes often under Windoze 7 on my HP machine. Curiously it runs just fine on a Mac (Fusion emulator and XP sp3). If thweather holds into next week I shall try it out Gosport-Guernsey and back.
I have found the best is SeaPro 3000 which is stable, easy to use and fast. It can use Navionics chart cartridges or a number of other chart packages, but not C-Map. However I don't know if I can export routes/waypoints to a plotter.
There is also something called BoatCruiser 2.0 which does use C-Map discs and is a real improvement on the C-Map planning software. Unfortunately far from cheap. Fugawi produce something which seems compatible with most plotters, but I haven't used it.
Hope this may assist.