How can I disable CTRL+ENTER and ALT+S in Outlook 2007?

I think you're trying to disable CTRL+Enter instead of Alt+Enter. Here are the instructions:

1. Select "Tools -> Options" from the main menu in Outlook
2. Click the "E-mail Options..." button
3. Click the "Advanced E-mail Options..." button
4. Look at the checkbox at the bottom

EDIT: For Alt+S, try reading this Technet article to shed some light on disabling shortcut keys: Disable user interface items and shortcut keys. You'll need to setup a group policy with the appropriate admin template. If group policy isn't an option, you should be able to edit HKCU\Software\Microsoft\Office\12.0\Outlook\DisabledShortcutKeysList\ in the registry.

!s::Return

in autohotkey would disable that key globally. You'll want to put it in a #IfWinActive block, but I don't know what Outlook's class names are, so I can't tell you that.

#IfWinActive, ahk_class [Class Here]
!s::Return
#IfWinActive

Use the bundled Window Spy to grab the class and plug it in, and that'll work :)

Outlook 2013

For future visitors, in outlook 2013 (maybe 2010), the option is at:

• File
• Options
• Mail
• (section) Send Messages
• CTRL + ENTER sends a message