Reference: Https://groups.google.com/forum/#!msg/opnet/OmOI_bstjTI/GhP-PRhpxEEJ
1-start-> All Programs, Microsoft Visual Studio, Visual Studio Tools, and then (either) Visual Studio C Omand prompt OR Visual Studio comand prompt x64 (DEPENDS on YOUR SYSTEM).
2-type The following comands, set INCLUDE and press ENTER, set LIB and press Enter and set PATH and presses Eneter.
3-copy This comands and the store it in a temporary text file.
4-go to the computer environment variables.
5-i think I won't have a variable for LIB or INCLUDE, so you need to create them.
6-set The values for those variable to the values shown in the Comand prompt JUST after the = sign.
7-make sure that all the values is copied as sometimes it takes only a single line to be copied.
8-finally and most importantly, if is running opnet as ADMIN then you'll need to add those variables to the US Er variables, and IF you is RUNNING OPNET as NORMAL USER then set those values to the system environment variables.
Finally, it's important to set up. In edit-and preferences, discrete Event Simulation, "Network Simulation repositories" is populated with the value "(Stdmod)". That's all you can do.
OPNET 14.5 + Windows 7 + Visual Studio 2010 A setup issue