You could try reading them in to the free office suite OpenOffice (www.openoffice.org) and then saving them as word2k documents.
Well, individually reading in old files is now do-able: I found a conversion routine under microsoft called wdsupcnv.exe that creates extra reference files in c:\program files\common files\microsoft shared\*.cnv that does convert "up" from Word5.0 to Word2000 when the (old) file is loaded.
BUT, that converts the old fiole.
How would I convert the previous reference file (in MSWord5.0) that does the same thing that autotext changes in MSWord 2000 and MSWordXP (MSWord2003 = MSWordXP as I understand MicroSoft's confusing designations!): when a new file is being written, autotext changes the typed-in phrase or text into a new formatted text string.