There might be a issue that keeps A: from showing up from Word, but count
yourself lucky. Because of the way Word creates temporary files, saving
files directly to a floppy (or opening files that are on floppy) makes
document corruption not only possible, but likely. While it might seem like
extra work, the "best practice" method is to save (and close) to your hard
drive, then use Windows Explorer to copy to the A: drive. When you want to
edit a file that's on your A: drive, reverse the process: copy to your hard
drive, and work on it from there.
Not only does this greatly reduce the chances for document corruption, but
working on the file will be much faster as well.