Hello. I am new to this forum. Have posted this to a Visual C++ forum too. They suggest I try a Windows forum. I have a small app created with Visual C++ running on Windows 7 Pro. It runs fine when executed from within the V++ IDE. It runs fine if I simply double-click on the .exe file. I would also like my users to be able to double-click on one of the associated data files (my own .spv format), and have the sim run taking that file as input. Was hoping that I could simply associate .spv files with my sim and that the data file would be accessible to main (argv, argc). It almost works. My sim is fired up when I click on an .spv file, and the correct data file name is recognized in main. However, I also get an error message panel from windows (?) listing the acceptable command line options such as -i, -bg2 -di, -na, -ti, etc. This panel interrupts the execution of my app. Once I close it everything runs fine. Anyone know what's going on here? I've been working for about 6 hours trying to iron this out (reasoning, guessing, forums etc). Any help is greatly appreciated.