You need to get into the Network Connections. How you do this is going to be different depending on various settings on your system or Version Of Windows.
The most common way to get there would be to click on the Start button, ->Settings, and then Control Panel.-> When the Control Panel opens Double Click on Network Connections.
Once you are in the Network Connections, right-click on your ADSL connection and select the Properties option. If you are not sure which connection is your ADSL connection, then you may need to try these steps a few times with different connections, until you get the icon you are looking for.
At the bottom of the General tab within the connection's properties, check the box labeled "Show icon in notification area when connected" and click the OK button. If this box is already checked, then uncheck it, click OK, open the Properties again, check the box, and click OK again.
This should return the icon you were searching for.