The Windows Installer is trying to uninstall something from AutoCAD 2011 and needs the MSI file from disc 1 to run the uninstaller. It could be a file in C:\Program Files\Common Files\Autodesk Shared ;however, I have not run into this problem.
Make sure you reboot your system if you have been running AutoCAD and want to install a new version of AutoCAD.
I strongly recommend installing all Windows updates, rebooting the system, not running anything else, then installing AutoCAD.
Kevin Moore Test Development AutoCAD Autodesk, Inc.