My link was based on the assumption you were using a wireless router and had a configuration similar to the following:
[modem]<-- wire -->[wireless router]<-- wire/wireless -->[pc]
Your router (at least according to you) is currently configured w/ WEP wireless security. That document will (as it states) “explain the difference between WEP, WPA, WPA2 and how to set up each of them”. You need to change your router’s wireless security type to either WPA2 (preferred) or WPA and update your wireless clients to use the same security type when they connect.
Granted that document uses a Linksys wireless router for illustration purposes, and you may be using a different make & model, but the same principles apply across all wireless routers.