Trouble uninstalling SQL Server 2012

Hi all, 

I am currently trying to uninstall my copy of SQL Server 2012 + SP1 (dreamspark) which may be corrupt, and install SQL Server 2014 CTP2. the only problem being, when i try to run the uninstaller or any copy of the original setup package, the application crashes with this error:

Description:
  Stopped working

Problem signature:
  Problem Event Name:CLR20r3
  Problem Signature 01:scenarioengine.exe
  Problem Signature 02:11.0.3128.0
  Problem Signature 03:50de6f4e
  Problem Signature 04:Microsoft.SqlServer.Chainer.Infrastructure
  Problem Signature 05:11.0.0.0
  Problem Signature 06:50de6f4c
  Problem Signature 07:20e
  Problem Signature 08:179
  Problem Signature 09:ZAGSF01GRLFWVJMY5S0U0HXSJJE2HDT4
  OS Version:6.1.7601.2.1.0.256.1
  Locale ID:3081

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will installing 2014 overwrite the 2012 installation?

any help will be greatly appreciated.

thanks

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From, Nathaniel Peiffer