Really? It is not apparent that I am asking how to do it within the context of a Nullsoft script?
Of course it is but I don't know the answer off the top of my head.
Referencing some other sources in your question would at least show that you did some kind of research before asking.
http://blogs.msdn.com/b/astebner/arc.../10008146.aspx is a very good starting point. If things have not changed for 2013 then there appears to be two methods; checking the registry or calling MsiQueryProductState. This brings up a new question, are you looking for a specific version/service pack or just any install? 32 or 64 bit?
http://stackoverflow.com/questions/1...2-is-installed also talks about keys under HKLM\SOFTWARE\Microsoft\DevDiv\vc\Servicing which might be interesting to look into.
A fourth method is
http://nsis.sourceforge.net/WinSxS_Q...y_is_installed but I don't believe this applies to the newer runtimes because they don't use SxS anymore IIRC.
I got all this information in less than 5 minutes with a simple google search.
I don't know if there is a canonical answer to what the best method is, you will have to do some more investigation and perhaps some testing. Once you decide on a method, actually doing the check in NSIS should not be that hard...