D-Link DWA-121 User Manual page 10

Section 2 - Installation
You will see a warning that says, Disabling the device will cause it to stop
functioning. Click Yes to disable the adapter.
When the adapter is disabled, you will see a red X over the icon that represents the
device. However, this does not mean you have removed it. Disabling the adapter
will not remove the drivers either. If in the future you would like to use the adapter,
simply right-click it and select Enable.
D-Link DWA-121 User Manual 10