When migrating from Windows Small Business Server 2003 to Windows Small Business Server 2008 you may find that the Exchange Information Store Service does not start automatically on the destination server after installing Windows SBS 2008. Because SBS 2008 is a global catalog server, when Exchange 2007 installed on a GC, some services like: Microsoft Exchange System Attendant, Microsoft Exchange Information Store may not start automatically, which is normal.
The cause of the issue is that Exchange services depend on following Windows Services:
NT LM Security Support Provider
Remote Procedure Call (RPC)
When any of these service do not start before Exchange tries to start Exchange services, the Exchange Information Store service cannot be started. You can either change the service dependencies, or you can add BootPause registry key to delay the startup of Exchange Server. Microsoft provides instructions to perform these steps in the following knowledge base article: http://support.microsoft.com/kb/940845/en-us.