Thanks for the suggestion of MenuApp.
I'm taking a look now -- one thing that caught my attention is:
MenuApp configuration is controlled by an "ini" file called MenuApp.ini, which is created automatically when you first run the program.
The file lives in your LOCAL_APP folder in a subfolder called MenuApp.
On Windows XP this will be:
"C:\Documents and Settings\username\Local Settings\Application Data\MenuApp".
This was sounding like bad news for my portable set-up. However, further reading turned up:
menuApp can be run from removable media like a USB drive.
To get this to work you need to put the menuApp ini file in the same folder on the USB drive as the menuApp.exe. menuApp will use this rather than the ini file in the LOCAL_APP folder.
The only annoyance is that it repeatedly replaces itself in the startup folder.
I was looking at the ini file and it looks to me like there is an 'AutoStart' setting under the [Server] section -- may be that can be used to disable this behavior.
As to applying to the issue of opening recently opened (closed?) Windows Explorer windows though, I'm not sure how I'd get that to work out:
MenuApp displays the contents of the folder in which it is run.
Although MenuApp does seem to have some way of listing Special Folders, this appears to be based on setting up a shortcut for each Special Folder beforehand:
MenuApp knows about some special folders which are displayed using a command line parameter.
The format for this is:
"C:\Program Files\MenuApp\MenuApp.exe" -X
where X is one of the following values: ...
If there were a folder on my system that continually got updated w/ shortcuts to folders (including Special Folders) I accessed recently it seems like that might be used toward the end in question, but I don't know of one. Or may be there is some way to apply this app appropriately that I'm not seeing...