Managing accounts
For many different reasons, a user account might become inactive. If a user leaves a company for a certain period of time or resigns, and you think that the user doesn't need access to the account or the resources, the best practice is to disable a user account until you're sure it's safe to delete it. If you want to disable an account, you can use either of the MMC Snap-ins. All you need to do is select the desired user account and disable it by right-clicking and selecting Disable or Disable Account, depending on which MMC Snap-in you used. If you enable a user account, the procedure is same, but the options are different: Enable or Enable Account.
The PowerShell cmdlets that need to be used for this task are Enable-ADAccount and Disable-ADAccount, and the command needs to be as follows:
Disable-ADAccount -Identity vladimir.stefanovic
Enable-ADAccount -Identity vladimir.stefanovic