Can please somebody tell me where to download Overlay patch for AutoCAD 2004???

Overlay patch?
 
You can find all the service packs and hot fixes on the Autodesk site: http://usa.autodesk.com/adsk/servlet/ps/dl/index?siteID=123112&id=2334435&linkID=9240618
 
But I didn't see one called Overlay patch.