As soon as you can, you will want to upgrade that puppy to 9.0. For starters, USB is not not supported under 5.2--at least the support was minimal if at all. Secondly, those old linux kernels have security holes you can drive a truck through, which should be a major concern if you are planning on being connected via DSL.
I'm not sure how DSL modems work, but if you can connect via ethernet instead, do so. It's the ONLY option available to cable modem users (Linux, of course). Of course, with a 2.0 kernel, USB isn't possible anyway.
You're on the right track--you just need a bit of an update, that's all!