I don't have a Windows specific way of helping you out, but I do have another idea.
I'm working on the assuption that this is an interactive things being you are accessing a floppy otherwise you can stop reading now!
Maybe instead of just dying if the pipe can't be opened, trap the error and send it to a sub-routine that prompts the user to insert/check the floppy etc.
If it fails a second (or some number of) times then exit with a nice "Can't access your floppy" message.
-THRAK
www.polarlava.com