Exchange 5.5 on Win2000

i didnn’t have any problem intalling exchange 5.5 on NT4. but when we migrated to win2000 advance server, it wont work… is there any chance for me to use exchange 5.5 on win2000 or do i really need to use exchange 2000 to enable of mail server? if it’s possible to use exchange 5.5, how do i set it up? if exchange 2000, how?