I can't find the duplicate on Server Fault (maybe it wasn't on here after all), but I used the following instructions when I went on holiday halfway through a migration:
As you probably know, you have a service called SBCore or "SBS Core
Services", which executes the following process:
C:\WINDOWS\system32\sbscrexe.exe. If you kill it, it just restarts –
and if you try and stop it you are told Access Denied.
If you fire up Process Explorer, you can select the process and
Suspend it, now we can start to disable the thing. Run regedit and
expand the nodes until you reach the following hive
click this, hit permissions and give the "Administrators" group on the
local machine full access ( don't forget to replace permissions on
child nodes ). F5 in regedit and you'll see all of the values and data
under this key.
Select the "Start" DWORD and change it from 2 to 4 – this basically
sets the service to the "Disabled" state as far as the MMC services
snap-in (and windows for that matter) is concerned.
Next, adjust the permissions on the file
C:\WINDOWS\system32\sbscrexe.exe so that EVERYONE account is denied
any sort of access to this file. Then go back to process explorer, and
kill the sbscrexe.exe process, if it doesn't restart –
Load up the services MMC snap-in and you should find that "SBS Core
Services" is stopped and marked as Disabled.