Windows Vista. PPPoE setup is done almost the same way a dial-up is created.
Start, Control Panel, Network and Sharing Center (you may have to switch to Classic View or go through Network and Internet to get to Network and Sharing).
Click on Set up a Connection or Network.
Click on Connect to the the Internet, Next.
(If it asks, "Create a New Connection")
Broadband PPPoE. Next.
Enter the username and password. Connection name is Cactus Computer.
Check Allow other People.... unless you have a reason not to.
Click the Connect button. At this point it will try to connect. If it fails (for instance, because your cable is unplugged or your wireless is not yet connected) choose Set up the connection anyway.
You may want to put a shortcut on the desktop. To do this, choose Manage Network Connections on the left, then right-click on the Cactus Computer and create a shortcut.