Right now when I double-click a STEP or IGES file it opens in SW. This works fine if SW isn't already open. But if it is open, the existing instance is ignored, and a new instance is opened. How can I get the STEP file to use the existing instance? I tried rerouting the Open command in the registry, but no luck. Adding "/dde" just makes the file open in a new invisible instance. Opening the swFileLauncher just gives an error message since it's only programmed to handle SW files. Any hints? Is there a command line parameter that will force SW/Windows to check for an existing instance before opening a new one? Thanks!