W7 users are expected to download Windows Live Essentials, which includes Windows Live Mail. (Microsoft can't supply it directly with Windows 7, as to do so would contravene EU anti-competition regulations):
http://explore.live.c...-other-programs?T1=t3
(Despite the reference to XP, that's the correct link for W7. Click on 'View system requirements for confirmation).
Outlook is supported by W7 but only, it seems, from Outlook 2003 onwards:
http://www.msoutlook.info/question/303
However that link suggests that you might be able to get around your current problem by installing Outlook 200 in a specific mode. Quote: "Outlook 2000 cannot be installed in Internet Mail Only Mode (IMO Mode) and should always be installed in Corporate/Workgroup Mode (CW Mode) to prevent a wab.dll error".
(Don't ask me how to actually do it though; I haven't got a clue!)
Chris