I followed the link above to the other post -
http://www.aximsite.com/boards/showthread.php?t=56580. Courtesy of MKREdit, the registry key is: HKEY_CURRENT_USER/software/microsoft/shell/taskswitch
I deleted not just the Registry values, but the entire keys. Although there is still a Recent Programs heading on the Start Menu, it isn't listing any programs.
The registry keys are numbered 0 through 9. If you want to limit the number of recent programs displayed rather than permanently wipe them all out, just delete some of the keys.
For example:
If you want only four recent programs listed, delete keys 4 through 9 and keep 0 through 3.
McGraw Hill publishes a Pocket PC book titled: "How to Do Everything with Your Pocket PC." You can get a PDF of the book. I haven't looked at it much, but it's 500 pages, so it may be helpful to some.