It might not suffice. I don’t believe the path to the compiler gets added by default on installation.
Basically do this:
with the path to the directory where CL.EXE lives… which should be by default what I stated above, assuming an x64 Windows 8 system:
C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\bin
If Mathematica still complains, please post the exact error… I haven’t tried to use CUDA from within Mathematica, but it would seem like it just doesn’t find the Visual C compiler from what you mentioned.
Perhaps this helps, assuming that’s what you’re using: