You may find yourself in a position where 21 days isn't enough to finish the migration, if you find yourself in this situation there are two methods for extending this limit.
The methods below should only be used as a short term solution as they technically violate the EULA, but needs must.
How to determine how many days you have left: http://blogs.technet.com/b/sbs/archive/2011/04/14/how-to-determine-the-number-of-days-left-for-sbs-2011-migration.aspx
Extend for another 7 days
This is as simple as moving the FSMO roles back over to the SBS 2003 server (http://support.microsoft.com/kb/255504)
From the SBS 2003 server open a command prompt and run netdom query fsmo - confirm the SBS 2011 server is currently holding the FSMO roles. The procedure below gracefully transfers the FSMO roles back over to the SBS 2003 server.
- ntdsutil
- roles
- connections
- connect to server SBS2003
- quit
- Transfer domain naming master
- Transfer infrastructure master
- Transfer PDC
- Transfer RID master
- Transfer schema master
Run netdom query fsmo and confirm that the SBS 2003 server now holds all of the FSMO roles. The time limit has now been extended by 7 days.
After the 28 day period (21 plus the 7 above) - Disable Shutdown
This method will prevent the source SBS 2003 server from shutting down indefinitely. From the SBS 2003 server transfer the FSMO roles back to the SBS 2011 server.
From the SBS 2003 server, download and run Process explorer: http://technet.microsoft.com/en-us/sysinternals/bb896653.aspx
Find and right click sbscrexe.exe and choose suspend.
Open regedit and browse to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SBCore.
Right click on SBCore and select permission, add the administrator account and give full control to this key and subkeys, click yes if warned.
In the right hand pane, change the "start" DWORD to 4 (from 2 default).
Now browse to C:\Windows\System32 and locate sbscrexe.exe. Right click, properties, security -> Add everyone and select deny for all.
Go back to Process explorer and select kill process, open task manager and confirm sbscrexe.exe doesn't restart.
