Why does my internet disconnect every 30 minutes?

Factual Questions
1

I have DSL, I use Windows XP, and my computer is hooked up to other computers via ethernet. All the other computers in the house are hooked up to the same connection, but mine is the only one that disconnects every half hour. Like clockwork, I have to reboot and then I get my connection back again.

What’s causing this, and how can I solve it?

2

Have you got your email set to check every half hour and then disconnect?

3

If not your email, maybe your anti-virus software is set to update automatically?
For some reason, mine keeps defaulting to 5 minute updates.