Well, I finally got the data cable working properly - since it’s a non-genuine part, it works in non-normal ways. Rather than being a USB cable, it detects as a “Nokia 5140 connected through Serial Cable.” Which is why it wasn’t working, because the software that is included with the normal PC Suite doesn’t include serial drivers and so forth.
I’ve been reading things on Nokia’s Discussion Boards with regards to what I can and can’t do with the phone, software updates and things that are to be played with, and it looks like the Series 40 OS is pretty simple, which means I can’t do much with it. I guess I’ll just have to get into programming for the phone in Java and see what I can do 🙂