I know how to set default programs in vista:
* Click Start, select Default Programs
* Click Set program access and computer defaults
* Click Custom, and select your mail client (for example, Windows Mail)
* Click OK
However, this doesn't work for me. When I do this (setting Lotus Notes as default mail client) and click OK, and go back. Nothing has changed. So I tried to reset IE as the default browser in custom. Same result. Click OK, change doesn't take.
Turned off UAC. Rebooted. Same result (or lack of result).
New machine. Notes 7.02. Office 2007 (symptom: can't send document by email from word 2007; all the menus to send email are grayed out).
Notes works as default email for everything I've tried except Office.