Ok so launcher.exe on it's own is targeting .NET 4.0 client profile, so it should run on Win8. It would pay to check the .dlls used in CoD and see if its the same.
I have been checking MSDN and I've read that in Win 8, .NET 4.5 has .NET 4.0 incorperated into it (this is a first).
http://blogs.technet.com/b/askcore/a...ework-3-5.aspx
I wonder if there is an issue with that version of .NET 4.5
I bought Win8 last night to try it out for myself. After I restored CoD in to my Steam library and ran it, it went to install .NET 3.5, problem is the installer hung. I don't know if it was the installer or that my net connection was really slow as my kids were complaining they couldn't login to thier Minecraft accounts. I'll check it all again when I get home.