Trying to install SQL 2012 Developer Edition to a new Windows Server 2012 R2 (or Windows 8.1) machine I was getting an Unhandled Exception immediately after running the setup.exe.
Turns out this is due to a user.config file that gets created by conflicting versions of the .net framework as described in this Microsoft Article: http://support.microsoft.com/kb/2681562
Fortunately, there’s an easy fix:
Open this folder: %userprofile%\AppData\Local\Microsoft_Corporation\LandingPage.exe_StrongName_ryspccglaxmt4nhllj5z3thycltsvyyx\126.96.36.199
Delete the user.config file.
Re-run your setup and you’re good to go.