The installation has rolled back and this this error appeared:
Error 1935: an error occured during the installation of assembly component
97F81AF1 -0E47 -DC99 -C8B3B9A 1E8E
HRESULT: 0x800736FD
I currently have Microsoft .NET Framework 4 Client Profile installed instead of Microsoft .NET Framework 3.5 Service Pack 1. Could this be the problem?