Hi Jungle_men,
Manually removal Exchange 2007 from Exchange Organization is not supported. You can know more information from these threads:
Remove a crashed server from Exchange Organization
http://social.technet.microsoft.com/Forums/en-US/exchangesvradmin/thread/634892a5-b3b3-46f2-bc67-824b664bf50f
For this issue, since your server is not exist in the domain, you can use Adsiedit to remove related entries for the old server.
CN=Configuration, DC= Domain_Name ,DC=com, CN=Services, CN=Microsoft Exchange, CN= <Organization_Name>,
CN=Administrative Groups, CN= Exchange Administrative Group (AGname), CN=Servers, CN=<Server Name>
Thanks,
Evan
Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.