All modems (why not buy a modem/wireless router combo, so you can go wireless with your laptop, phone and tablet?) will work with your XP system (and, in fact, with Linux and Apple also).
The most important thing is that it is able to work with AT&T.
I need a new modem, mine is dying. How do i know which one will work with my system. I am using xp on my dell. I am using AT&T 3mbps DSL service. My current modem is a Motorola 2210-02 DSL Modem. It is okay, but i just might have gotten a good one cause a lot of people had trouble with theirs. The tech at AT&T suggested a Netgear 7550. It has gotten some poor reviews. I would just like the correct modem that works well and lasts a while.