Which Windows 8 do you have installed?
Visual Studio 2012 RC products are not supported on Windows 8 Community Preview or Developer Preview.
You must have Windows 8 Release Preview installed to support VS 2012 RC.
Only the Release Preview has the .NET 4.5 version you need.
Download the Win 8 RP here:
http://windows.microsoft.com/en-US/windows-8/download
