I briefly considered signing up with TPG for ADSL, but eventually passed them over due to their lack of Linux support. If the modem you have is the one provided by TPG, then it's a crappy USB DSL modem -- I did a bit of research on that particular model, and it turns out that it's a real pain to get working under Linux.
You might be interesting in this link, however:
Good luck. Sounds like that particular modem is a bit of a horror to setup.
If you're gonna stick with Linux and aren't locked into a contract with TPG, let me give you some free advice: Check out Internode (www.internode.on.net
). They specifically support Linux and have better prices than TPG (considering the services they offer). They don't provide a free DSL modem, but you can get a preconfigured D-Link DSL-300 (this one's ethernet based, which is why it works and the DSL-200 doesnt) that works great with Linux and is worth shelling out for.