C-Compiler Error in Matlab/Simulink

When trying to run a MATLAB FUNCTION Block I get the same error, which is...

"Unable to locate a C-compiler required by Stateflow and MATLAB Function blocks. Use 'mex -setup' to select a supported C-compiler."

I downloaded the Microsoft Windows SDK for Windows 7.

When I run mex -setup and select y, it states "No supported SDK or compiler was found on this computer."

It then has "Error using mex (line 206)"

What steps do I need to take to have MATLAB recognize that I've already downloaded a compiler?

Thank you.