Here is a quick powershell command to find all users inside of your Active Directory domain that have been marked as disabled (this will exclude disabled computers):

Get-ADUser -Filter {Enabled -eq $false} | FT samAccountName

Additionally, you can specify which additional options you would like to show by change the filter table command we are piping the results to.  For example, this command will show the samAccountName, first name, and last name of the disabled users.

Get-ADUser -Filter {Enabled -eq $false} | FT samAccountName, GivenName, Surname

If you want no formatting whatsoever and have AD spit a bunch of information back at you, try running just the Get-ADUser part with the filter applied.

Get-ADUser -Filter {Enabled -eq $false} 

The following command below can be used to pull a list of disabled users and computers:

Search-ADAccount -AccountDisabled