引用：https://groups.google.com/forum/#!msg/opnet/OmOI_bstjTI/GhP-PRhpxEEJ
1- Start-> all programs -> Microsoft Visual studio -> Visual Studio Tools -> then (either) visual studio comand 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 press eneter.
3- copy this comands and store it in a temporary text file.
4- go to the computer environment variables.
5- I think I will not 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 are copied as sometimes it takes only a single line to be copied.
8- FINALLY AND MOST IMPORTANTLY, if you are running opnet as ADMIN then you will need to add those variables to the user variables, AND IF YOU ARE RUNNING OPNET AS NORMAL USER THEN set those values to the system environment variables.
最后，重要的是要设置。在Edit -> Preferences里，All -> Discrete Event Simulation里，把“Network Simulation Repositories”的值填上"(stdmod)"。这样就可以了。
来源：oschina
链接：https://my.oschina.net/u/228604/blog/306651