If you are migrating your Small Business Server 2003 to Server 2008 or 2012, after making your new server a new Domain Controller, your SBS 2003 will start to shutdown after 21 days. If you are planning to take longer than that for your migration, you can disable the SBS Core Service. This is not easy since if you end this process it will restart. Fortunately, you can follow these steps:

• Download Process Explorer from this link.
• Run Process Explorer and suspend the sbscrexe.exe process.
• Using RegEdit, navigate to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SBCore
• Right-click on SBCore and select Permissions.
• Add Full Permissions for your Administrator account and replace permissions on child objects.
• You will see the Registry Keys for SBCore (if not, refresh).
• Change the Start REG_DWORD Key from 2 to 4. This will disable the service.
• Browse to the file C:\Windows\System32\sbscrexe.exe and add the Everyone group with Deny All permissions.
• Using Process Explorer, Kill the sbscrexe.exe process.