If your computer has no Ethernet port, you need a USB adaptor in order to make use of your DSL connection. Wireless network connections pick up wireless waves sent out by a router that shares a DSL Internet connection between multiple computers. If either of these devices is disabled, it cannot be used by Windows, but enabling both a wireless network connection and an Ethernet adaptor makes it usable--and the process is the same for both Ethernet adaptors and wireless network connections.
Click on "Start > Control Panel > Network and Internet > Network and Sharing Center > Manage Network Connections."
Click on the Ethernet adaptor or your wireless network connection (whichever you need to enable) with your right-mouse button.
Select "Enable" from the right-click menu that appears. Windows will now enable your device.