Depending on how your dialer is invoked, you may not receive a 3-digit DUN (dial-up networking) error code when your computer fails to connect, but you'll need one for troubleshooting connectivity problems. Here's how to get an error code: In Windows Vista: Click on Start. Click on Control Panel. Click on Network and Internet, then click on Network and Sharing Center. On the left under Tasks, click on Manage Network Connections. Double-click on your BMI icon and then click the Dial button. In Windows XP: Click on Start. Go to Connect To, and select Show All Connections. Double-click on your BMI icon and then click the Dial button. In Windows 2000: Click on Start. Click on Settings. Click on Network and Dial-up. Double-click on your BMI icon and then click Connect. In Windows 98: Double-click on My Computer. Double-click on Dial-up Networking. Double-click on the BMI icon and then click Connect. Note: OSX (Apple) has different error codes than Windows.