Egg on my face department regarding my original posting, (disabled functions in Windows Explorer File Type management), but my thanks to Frederick Navarro, <[log in to unmask]>, for several suggesti6ons of possible solutions for the "problem" I described.  As he pointed out, I neglected to mention that the PCs in question are running Windows XP HOME edition, not Pro, meaning that gpedit.msc is not an available Policy Editor option for tinkering with relevant registry keys.  

The greater omission was not to include in the problem summary that the issue was with non-administrator logins.  I simply wasn't aware that one of the restrictions placed on these users is that they are not permitted to make changes in file associations.  This change function seems innocuous enough but apparently has proven to be a source of consternation to administrators of open labs, etc.  The fact that the restriction does not appear to be explained on local or on-line Help references, in Microsoft's KB, or Developers' forums.  There also appears to be no work-around to grant partial authority, at least not in XP Home Edition. 

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