emacs and SUBST command

["Mickey Ferguson" <MFerguson@plantcml.com>]

I've discovered that in the SUBST command, one can use not only a letter but a number for a drive designator.  For example, you can use

    SUBST t: C:\Temp

which is the usual and familiar way.  However, one can also use

    SUBST 1: C:\Temp

Both are valid.  However, within emacs if I try to reference a file that's in C:\Temp, say, C:\Temp\Myfile.txt, by using the 1:\Myfile.txt notation, emacs doesn't find the file.  It can't work with anything under the 1: "drive".  Additionally, if my current drive is set to 1: and I try to start emacs, it crashes.

I'm currently using emacs 21.3.1 on XP SP2.  Is this something that's fixed in 22.x, the current version, or is this simply something the authors weren't aware of and/or didn't anticipate?