Not able to install AutoCad 2000i

One of my user uninstalled AutoCAD 14 and AutoCAD 2000 from his PC which he installed and the process was not complete,
now I am trying to install 2000i licenced copy and it gives me an error before I type the seriel no. “The following serial number you entered is not valid, try again”.

Any clue why it is ?

Thanks in advance