Disable users using Active Directory Users and Computers

Using the ADUC console you can easily select one or more user accounts to disable.

To disable a single account just browse to the organizational unit, right-click on the account then select disable account. 

To disable multiple accounts just hold down the ctrl key and select multiple accounts then right-click and select disable account. In this example I just randomly selected multiple accounts from the Accounting OU. 

As you can see it is very easy to disable user accounts using the ADUC console. This method works well if you have a few accounts that are in the same OU. If you have a big list of accounts that are in various OUs then you will want to use PowerShell.