When creating a dial-up connection in Windows for VPOP3 to use, the important thing is that you must create the connection configured so that anyone can use it. If you don't say that anyone can use it, then it will just be associated with the 'current user'. Because VPOP3 runs as a service in a different user account, it will not be able to see any connections created for the current user. If you create the connection so that anyone can use it, then VPOP3 will be able to see and use it as well.
In Windows, open Control Panel
Select Network and Internet
Select Network and Sharing Center
Select Set up a new connection or network
Select Connect to the Internet - Set up a broadband or dial-up connection to the Internet and press Next.
If it says 'You are already connected to the Internet' choose Set up a new connection anyway.
Choose the appropriate method or modem
Enter all the appropriate details provided by your Internet provider.
You MUST check the Allow other people to use this connection box.
Now, VPOP3 should be able to see this new dial-up connection.