I've been having path problems lately (bar total path length this is not related to ifort) - so I went a-digging.
The redistributable installer adds the following paths to the head of the system path:
[plain]%INTEL_DEV_REDIST%redist\intel64\mpirt
%INTEL_DEV_REDIST%redist\intel64\compiler
%INTEL_DEV_REDIST%redist\ia32\mpirt
%INTEL_DEV_REDIST%redist\ia32\compiler[/plain]
Beyond the resulting excessive comsumption of precious system path length - all good.
When you start a command prompt for a particular ifort version and flavour, it adds the equivalent of the following to the head of the path
[plain]%IFORT_COMPILER14%redist\intel64\compiler[/plain]
This means that the redistributables for the targeted version are picked up in preference to the system installed version - all good.
The command prompt script also adds the following to the tail of the path:
[plain]%IFORT_COMPILER14%redist\intel64\mpirt[/plain]
This is shadowed by the system installed version. If I follow what is going on correctly, bar differently named exe or dll additions to the targeted version directory, it would appear to be mostly decorative - hence if you are targeting a particular ifort version different to the installed version of the redistributables, your development testing will use a mix of ifort version bits. Is there a reason for this?
