Omnet + + problem

Hello
I have many problems with the simulation software omnet + +, I start myself by trying to test a small sample to get an idea about the execution.
For that I wrote back in the commands:

opp_nmakemake

For Responses I have the following:

opp_nmakemake: use-f to force overwriting exiting Makefile.vc

then I run the command:

NMAKE-f Makefile.vc

as expected NMAKE is not recognized as internal command.

what is the solution for this problem and what is needed for omnet configuration or installation of a tool (I have already installed VisualC + + toolkit)
thank you for any help and advice.

Before starting to use OMNET + + you must install MS. Visual C + + 2005 Edition Expess, then install the version 3.2 (binary version) and after downloading.

Good luck.

Check path of opp_msgc. Problem was that I had an older version of opp_msgc installed. To verify path, type 'which opp_msgc'

I just found the solution (for omnet version 4)
I will summarize the steps: First, you must download and uncompressed omnetpp-src-4.0RC1-windows.zip here's the link: http://www.omnetpp.org/filemgmt/viewcat.php?cid=2

Then you must start the executable mingwenv.exe which appears and you will see a window that looks back for invitation command and it asks you to execute the command '. / configure "after" make "made in the order it will take some minutes, the simulator is ready for use. if you want to run the IDE to use graphic omnet then you must copy the directory in the ide java virtual machine and run the jre executable omnetpp.exe