If you have backed up your system state data (Active Directory Database) then you can restore that deleted computer account. Just make sure that the system state data has not yet exceeded the tombstone value.
To restore the deleted computer account, reboot the the AD domain controller, press F8, choose Directory Services Restore Mode,(you must know the password which you inputted in the system when you perform a dcpromo)>login using that administrator account and password. Restore the system state data using the ntbackup utility.Do not restart the system yet when prompted. Open a command prompt window, type in the ntdsutil command, type "auth rest" (for authoritative restore), type in "restore subtree + DN (DN is the location - Cn=computername,Cn=computers,DC=microsoft,DC=com). If you have type in the right container, there should be no problem of restoring that deleted computer account.
Restart the system normally, and verify if the computer account has been restored.