Explorer for some reason appears to visit each subdirectory (at least both its MFT entry and its actual data payload) in the expanding parent and may perform additional processing as well, since it can process them at only around 20 per second (which means that expanding a directory with 1,000 or more subdirectories can take a minute or more, during which Explorer is frozen).
XP and later versions of Windows do not suffer from this problem in Explorer, and it’s hard to imagine why Win2K’s version acts that way (since it can expand such a parent directory in the RIGHT-hand pane almost immediately). I’ve tried disabling options like ‘display compressed files and directories in a different color’ just in case they were forcing this behavior, but so far to no avail.
Just a minor annoyance in an old system, but I’d be grateful if anyone knows how to eliminate it.