I want to use IC13 for new projects and compile old ones with IC11, so I want to keep two compilers on my machine and use them in different projects(maybe even within single solution in Visual Studio). I tried to install Parallel Studio XE 13 without uninstalling IC11. When I do this, Visual Studio no longer sees IC11, when I try to open IC11 project, visual studio attemps to convert it to new IC13 format right away. Seems like IC13 not just overrides but overwrites all settings for Visual Studio, because when I uninstall Parallel Studio XE 13, there is niehter Intel C++ toolbar in VS nor IC11 projects are able to open.
Are there any manuals or tips on how to set this up correctly?
For integration of one update version each of ICL 12.x (xe2011) and 13.x (xe2013) it should be relatively easy, remembering that only VS2008 and 2010 (Pro and above) are supported for integration of this range of ICL versions. If installation of xe2013 causes xe2011 to disappear, it seems like a buglet, but you should be able to repeat the xe2011 installation (at least if you don't try to go back to the original update 0) and have both available.
You would need to check which ICL version is selected in Visual Studio, in case it defaults to the last one installed.
If you don't use the same VS version for both ICL installations, you can expect an attempt to update your project when you open it under the newer environment. I suppose the solution for that would be to keep your older projects in separate folders.