From:
http://www.cmz727.com/alan/6700/6700.htm
Here is the registry hack for the softkeys on the today screen:
ALWAYS BACKUP YOUR REGISTRY FIRST
To change the softkeys on the Today screen
The left-hand softkey settings are at 'HKEY_CURRENT_USER\Software\Microsoft\Today\Keys\1 12', the right-hand softkey
settings are at 'HKEY_CURRENT_USER\Software\Microsoft\Today\Keys\1 13'
The 'Default' string value can be changed to whatever text you wish to have displayed
The 'Open' string value can be changed to the program you wish to run when the softkey is pressed
For example, to change the left-hand softkey to start the Messaging program (text messages and emails) you would set:
HKEY_CURRENT_USER\Software\Microsoft\Today\Keys\11 2\(Default) = Messaging
HKEY_CURRENT_USER\Software\Microsoft\Today\Keys\11 2\Open = \windows\tmail.exe