Here is a 90% solution (will stop the install message, but will still get a nag message the first time you start Outlook after logging in)
Use Regedit and go to
HKEY_LOCAL_MACHINE\SOFTWARE\Clients
Change the default value for Calendar, Contacts, Mail, and News to "Microsoft Outlook"
In the HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\Microsoft Outlook entry add a Type Reg_SZ entry named "MSIComponentID" and give it a value of "{FF1D0740-D227-11D1-A4B0-006008AF820E}"
This will stop Outlook from trying to "setup" each time, but you will still get a message about not being the default client the first time you open Outlook after each logon. I'm still trying to figure that one out.
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frmsrcurl:
http://msgroups.net/microsoft.public...0-on-Windows-7