If you had previously had AutoCAD 2011 installed this may happen. Is AutoCAD 2011 listed in the Add and Remove programs or Programs and Features list? If so try uninstalling it or follow Travis’ advice on using he Windows Installer CleanUp Utility in this thread. The Revo Uninstaller is another popular alternative. It is mentioned in this other thread as well.
If you continue to have trouble let us know.
Douglas Lauritsen, Autodesk Product Support
I'm having the same problem. AutoCAD 2011 is not listed in Control Panel>Add/remove programs. I have gone through this entire process:
which deletes registry entries, program files, common files, almost any thing I can imagine that would have a trace of an AutoCAD file in it. Still nothing. I went as far as deleting every search result I could find with the words autocad. Still when I try to download an educational version of autocad 2011 its says autocad is still installed... help