Sadly, with Win7, it no longer functions.
I think that ToDo.com (and CED.com etc) are 16-bit applications and the CPU can/will not run 16-bit code.
I found DosBox after reading this thread (Post at Tuesday, October 27, 2009 4:18 AM) in "Microsoft Answers".
ToDo.com is working; there may be a better solution, but for now I'm happy.
(later)
It comes with 30 pages of documentation:
1. Quickstart
2. Start (FAQ)
3. Command Line Parameters
4. Internal Programs
5. Special Keys
6. Joystick/Gamepad
7. KeyMapper
8. Keyboard Layout
9. Serial Multiplayer feature
10. How to speed up/slow down DOSBox
11. Troubleshooting
12. DOSBox Status Window
13. The configuration (options) file
14. The language file
15. Building your own version of DOSBox
16. Special thanks
17. Contact