Let me try to clarify...
Code:
WinXP machine, connected to internet
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hub
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Linux machine, you're trying to connect
Right? The Linux machine is trying to connect to the internet through a Windows machine that's sharing the connection?
If so, then you shouldn't be using PPPoE or any other ADSL software on the Linux system. Just straight DHCP. If you can ping the XP machine, and the XP machine can ping the Linux system, then not being able to connect to the internet on the Linux machine means the XP machine is badly configured.
Have you bridged the connections?