Occsaionsly, however more frequently in development environements since they are subject to more ad-hoc, proactive rebooting, you will see the following message during start-up:
This totally freaked out my client this morning when it happened in a siloed, development environment (which generally are considered to be disposable) . The error 20% of the time for me has been a NTDS database becoming
corrupt. The NTDS database in Active Directory is the workhorse, deriving it’s name from old NT Directory Service days. The other 80% is a device problem, which can be very common with VM environments (check the secondary IDE controller).