Thanks for the advice, but I found the answer when I checked a link on the "Scripts" page of the Kixtart homepage called www.virtualdr.com. They have discussion groups just like this one for NT/2K/9x/ME/... 
The solution is to delete the ShellIconCache file from the system directory (c:\WinNT) and reboot the computer. This may have to be done several times, but it finally works.
