I'm trying to write an installer stub for my VB programs since QB 4.5 compiles to a real EXE albeit a 16-bit one. Here's what I need to do (I think) after the user extracts the contents of a ZIP file as if they downloaded a setup from my site.

1. Get the windows\system dir
2. See if the VB runtimes exist there; if not copy them from the current directory
3. Shell out my full-blown VB installer now that VBs dependencies are copied
4. Exit automatically

But here's the problem:
1. What's a way to determine if a file exists in QBasic, considering that error trapping doesn't work in functions or subs?
2. What's a way to get the Windows directory?