Oh, I don't know. I think it's amazing what you can't find if you don't look
exactly. Although, in all fairness, I didn't find anything relevant using the exact title of this thread on google.
However, with a few basic modifications:
http://en.wikipedia.org/wiki/File_Manager_%28Windows%29It isn't really the difference between windows 98's file manager and NT's, but rather windows 3.1's (which is the same one used in 95 and 98) to NT's.
Also it would help if we knew if this meant the actual Filemanager (winfile.exe) or windows explorer.