(it's brand new... but from a local computer shop. i hope this isn't a silly question, but are all serial cables that have female 9-pin ends on both sides "null modem" cables? it's not like i could have a wrong type of cable is it?)

It's very likely that you have the wrong type of cable.

See if you can get hyperterminal working, for both send and receive, with the old drive in place. If not, you've got serial port or cable problems which need to be solved before you can go any further.