migrating away from SBS 2003 to windows 2008 and exchange 2007

[Christopher]

I am trying to migrate from SBS 2003 to Windows 2008 and Exchange 2007. Someone told me to go for the full versions and not SBS/EBS 2008. I am going to install a Windows 2008 DC and another Windows 2008 box for exchange 2007. From some other post, I found the below methods:

1. If we want to join this new Windows server 2008 to the current domain as an additional DC.
2. We can use FSMT (File Server Migration Toolkit) to migrate files and folders to the new DC.
3. We can also use USMT (User State Migration Tool) to migrate user profiles to the new DC.
4. We can install Exchange 2007 on the new Windows Server 2008 server.
5. For this is a migration issue, just move the mailbox from former Exchange Server on SBS to Exchange 2007 with new organization. If you want to keep the organization, try to do the transition actions.
6. Lastly, demote the old SBS 2003 and make it offline

Till step 5 everything is fine, but I want to know why I need to setup a new organisation and what the "transition actions" are? Thanks for any suggestions.

[Jerry]

I dont understand what you will gain by moving away from SBS 2008 or even EBS 2008 unless you have grown beyond 300 desktops. You have not specified any other reasons. I think that why you create the new organisation is because to prevent having to do the steps of removing the first Exchange server in an Organisation.