If you download and install AutoCAD, e.g. v2012 or v2014 on Windows8, windows 8.1, it is highly possible that you are not so lucky: the installation starts, and then suddenly terminates, showing that AutoCAD is NOT installed!
Checking the log shows that, maybe, it is due to the lack of Dotnet 4.0 on your windows system, where Dotnet 4.5 already shipped and installed. You cannot reinstall Dotnet 4.0, as .net 4.5 is already there!
The solution is to modify the SETUP.INI file and remove the PREREQUISITE related to .Net, as outlined here in Autodesk forum. A quick solution is to download below SETUP.INI and overwrite it in the AutoCAD setup package.
Download the updated SETUP.INI here.
Rerun the setup! That is it!