You might try creating a new connection and set it as default. If it's working, you can get rid of the old one. For details, read one of the below articles:

Q305549 - "HOW TO: Configure a Connection to the Internet in Windows XP Professional"

Q310410 - "HOW TO: Configure and Use Dial-Up Connections in Windows XP"

Q283070 - " HOW TO: Create a PPPoE Connection in Windows XP"


Good Luck,

Cetin


Trying to unweave, unwind, unravel
And piece together the past and the future,


T. S. Eliot