I find that as a novice coder, the powershell community has a lot to offer in the way of simplifying admin tasks. For managing user accounts (and othe AD objects), the powershell commands for Active Directory from Quest Software works best (
http://www.quest.com/powershell/). Once you have the snapin installed and loaded, try this:
$cutoffDate = (get-date).AddDays(-180) #replace 180 with however many days you want to go back
Get-QADuser -Disabled -LastChangeBefore $cutoffDate | foreach {remove-qadobject $_ -force -whatif}
Notice the segment of code that actually deletes the accounts has the "-whatif" parameter set. I suggest you test this code as-is to ensure you would only be deleting the accounts you want. If you are sure the list of users is what you want, remove the "-whatif" parameter and run it again.
-PseudoAdmin