To disable automatic dial completely (means no program can automatically
dial, however you can do manually.)
1. Right click the My computer icon (Desktop), open Manage/Services and
Applications/Services.
2. In the right pane scroll down to Remote Accces Auto Connection Manager
and double click it.
3. Use the Startup type drop box and choose Disabled.
Also see:
Modem Automatically Attempts to Establish a Dial-Up Connection When You
Start Your Computer or Start a Program