
I have been using the JOIN command for many years now, mostly with good
success in duplicating unix-style file mounts.  You will hear lots of
people cursing JOIN because they confuse it with the dos APPEND command
(a truely gnarly hack), but don't believe them.  You also will hear
people saying that Microsoft recommends that you not use JOIN.  But, in
Microsoft's Windows 4 Workgroups Resource toolkit, the following appears:

  "JOIN, an MS-DOS utility, works fine with Windows for Workgroups 3.1 if
  you do not change the state of the joined drives during a Windows for
  Workgroups 3.1 session. This includes adding or removing joined drives
  from within Windows for Workgroups. We recommend that you do not use
  JOIN when running Windows Setup or Windows for Workgroups 3.1."

Within this caveat, JOIN appears to be valid under windows.  However, I
have found a couple of applications that don't deal well with filesystems
that have been "mounted" using join.

In particular, the worst offender is Word for Windows 2.0x.  It gets very
confused when you edit and then try to save a file on a joined drive. It
wants to create the saved file as ~NNNNN.tmp in the current dir, then
delete the old file and rename the ~NNNNN.tmp file to the *.doc file.

Unfortunately, WfW usually writes the ~NNNNN.tmp file in some idiotic
place other than the current directory (often in the root dir of the
joined filesystem, but not always).  Then, after deleting the original
*.doc file, it can't find the ~NNNNN.tmp file to rename it.  Unless you
search your disk systems, the document is gone.

I have also found subtle problems using the MKS toolkit from a DOS box
when JOINed filesystems are present.  I used to join c:\temp with a 4meg
ramdisk, but MKS sometimes gets confused when doing an "ls" on the c:\temp
dir, and misses some files in the temp dir.  (This is difficult to 
reproduce, but it goes away totally when JOIN is not used.)  I think
this is a Windows problem, rather than MKS's, since it works OK under raw
DOS.

So, I would suggest that you can use JOIN, but be aware that it may not
be as robust you would like.

Wouldn't it be real great to "mount" network drives (i.e. Z:) under the main
file tree, rather than having all those darned drive letters? Unfortunately,
JOIN won't let you do it.  There was talk on the net about a simple patch
to let JOIN work on network drives, but I don't remember the source.

It's too bad the JOIN command is not better implemented, since it would
avoid using all those stupid drive letters.  I realize that MessDos was
meant for casual, even ignorant users, so "mounting" all the drives in
one file tree might be confusing. But, it looks like MS is going to carry
this over into windows NT (another OS meant for casual, even igorant 
users -- NOT!).  With all it's old family system baggage, maybe MS needs
a recovery group so they can get on with life :-(.
