You are unprotected if the radio butto next to "Disabled" is selected.
You don't say what your wireless PC is using a built in card or USB dongle. of the security options WPA is stronger than WEP so recommend that assuming your PC supports it that you use this option.
Also recommend that you use a network cable connection between PC and router to make changes to security settings. If you use a wireless link and things go wrong it can be hard to re-stablish connection.
Select the WPA/WPA2 option and select Pre-Shared key as the authentication type. Now enter a key made up of at least eight letters, numbers, symbols. Make sure that you remember it. Click Apply Changes.
You will have to make sure you set your PC wireless connection to the same security WAP and enter the same key before you will be able to connect.
Belkin manual explains all See from Page 48