I have noticed that there was a huge Microsoft folder under c:\users\myuser\app\local\microsoft.
It was like 30 gb.
Since I have a SSD driver I could not leave it at this location and had to move it to a different drive.
Now in Xamarin Studio I am getting the error
C:\Program Files (x86)\MSBuild\Microsoft\VisualStudio\v12.0\AppxPackage\Microsoft.AppXPackage.Targets(9,9): Error APPX1639: The file 'Windows.props' was not found. Additional information can be found at "http://go.microsoft.com/fwlink/?prd=12395&pver=1.0&plcid=0x409&ar=MSDN&sar=PlatformMultiTargeting&o1=C:\Program Files (x86)\Microsoft SDKs\Portable\v12.0&o2=Portable". (APPX1639) (MyApp)
The link that is mentioned in the error message is invalid.
Does anybody know how I can solve this problem?