about how your laptop connects wirelessly to your desktop. Obviously your laptop has a wireless adapter, but you say your desktop is connected to the LAN by ethernet. Where/how does the LAN connect to the internet? What equipment specifically is at the "other end" of the wireless connection from the laptop and what is it attached to? What is the nature of the wireless connection to the desktop - infrastructure or adhoc?
When we have a clearer picture of your configuration we should be able to give some advice.
my laptop is connected wirelessly to my desktop. My desktop has a broadband internet connection via the LAN or ethernet cable. I would like to find out how to share this connection to be able to use on my laptop aswell. help is greatly appreciated. thanx.