Officially Outlook 2000 does not work with Exchange 2007.
Is there any workaround to get Outlook working with Exchange 2007 nevertheless?
I have seen mixed reports on this, some users have reported that Outlook 2000 works fine with Exchange 2007, aside from the occasional error, where as others say they can only get connected if they use IMAP or POP.
Exchange 2007 uses RPC over HTTP by default, which Outlook 2000 does not support and will be the main source of the problems. Also to use older clients (2000, XP, 2003) you need to ensure you have public folders enabled.
You may recieve an error about SPA authentication, if this is the case follow the steps in this article.
Finally, this article has a number of steps that may help in setting this up.
However I would suggest the best option is to upgrade to a newer version.
There is a way to connect Outlook 2000 with Exchange 2007. Its not POP. Here are the steps I explained. Mails, Calendars, GAL working OK Step by Step guide to Outlook 2000 with Exchange 2007