If you will not be in Boston this weekend you can still row the Head of the Charles (and other races) by using a program called ergTour. It uses the Concept II Model D rowing machine to guide Google Earth along the race course.

Instructions
1.Start Google Earth and let it initialize. It is very important to do this first.
2.Connect the PM3 to the PC via USB cable.
3.Select your workout.
4.Run ergTour.
5.Start rowing.

Note: It is very important to have the Concept II PM3 connected before running Erg Tour.

Full instructions are in the documentation, including command-line options for creating a file for your own river. The program is installed by downloading and executing this setup.exe.

The program is free but will run for 45 days only.

Enjoy!

Edit:
11/04/2006 Erg Tour Version 0.5 uploaded. Note that many command-line paramters have changed. Also now includes Head of the Charles, Head of the Cuyahoga, and the Doggett’s Coat and Badge
10/22/2006 Renamed the program to Erg Tour and included a second map.