Network Administration: Windows User Account Enablement
In Windows Server 2008 if you want to temporarily prevent a user from accessing the network, you can disable his or her account. Then you can enable the account later, when you’re ready to restore the user to full access. Here’s the procedure:
Log on as an administrator.
You must have administrator privileges to perform this procedure.
Choose Start→Administrative Tools→Active Directory Users and Computers.
The Active Directory Users and Computers management console appears.
Click Users in the console tree.
In the Details pane, right-click the user that you want to enable or disable. Then choose either Enable Account or Disable Account to enable or disable the user.