Resolved.

When copying a simple installation's HIERARCH.PM file to a new installation, pmail will re-assign the unique ID of the primary mailbox.  It is a simple matter to do a find and replace on that unique ID.  

Example:

1) Delete the HIERARCH.PM file from the new installation, restart pmail, exit pmail and then look at the first line of the file, which will be something like:

 2,1,"5F242154:My mailbox","","My mailbox"

 2) Copy the old HIERARCH.PM file into the new installation.  A few lines from my old HIERARCH.PM file look like this:

 2,1,"56A33625:My mailbox","","My mailbox"

1,1,"1F533666:Tray1","56A33625:My mailbox","Tray1"

0,0,"1CF29095:0EFA:FOL132AA","1F533666:Tray1","Folder beneath Tray1"

0,0,"0E562976:3863:FOL031F0","56A33625:My mailbox","Folder In Mailbox - Not in Tray"

3) You would then find and replace each occurrence of 56A33625 with the new installation's unique ID for the mailbox (5F242154).

4) Save the HIERARCH.PM file into the new installation and restart pmail.

I don't know why, but pmail stopped working a few days ago.  By stopped working I mean that when I clicked on the shortcut to open pmail, it thought for a second and then aborted with the message about windows being forced to close the program.  That is background information.  I'm not interested in figuring out what that problem was, because I've moved on.

I put another installation of pmail on my computer and moved the .cnm file, the .pmm files and the .pmi files over.  Worked fine except for the fact that my folder hierarchy was lost (as expected).  I then moved a copy of HIERARCH.PM over and bad things happened.  Now, my folder view shows about 30 folders (instead of the approximately 2200 that exist).  If I obliterate the HIERARCH.PM and restart pmail, all is well in the sense that I get my 2200 folders back, but as expected, I have 2200 folders that are in desparate need of reorganizing.

 So, did I miss a step? Do I need to move another file from my old pmail installation other than HIERARCH.PM in order for pmail to construct a hierarchical view from the HIERARCH.PM file?

 Thanks

mike