I need to inquire if Video for Windows has been installed before
attempting to play an AVI file. How can I do this?
All versions of Windows keep track of "file associations". These are the things that make it so when you double-click a "doc" file you fire up Word or a "txt" file fires up Notepad. I'm not familiar with Video for Windows but I'm pretty sure it associates itself with the "avi" extension.
Check through the WIN.INI file (for Windows 3.x) or the registry (for Windows '95 or NT 4.0) to look for the "Associations" section. Look for the "avi" association. If you don't find it, it's an automatic "no". If you find it, look what it's associated with. If it's Video for Windows, it's a "yes", if not, a "no".