I have Intel® Parallel Studio XE 2019 Update 1 Composer Edition for Fortran Windows* came with Visual Studio 2015 Shell (Integrated), which is now at Update 3.
I need to rebuild a C/C++ program compiled with Microsoft Visual Studio 9 (2008). Is there a way to add MS C++ into my VS 2015 Shell, so I can use the existing .sln? Or, if I install MS VS 2017 Community, will that affect my Vs 2015 Shell/Fortran?
No, you can't add MSVC to VS2015 Shell. But installing VS2017 Community won't affect your VS2015 Shell. You could then, if you choose, do a "Change/Modify" on Intel Parallel Studio and let it add VS2017 integration.