ICS through wireless

Here is the setup. At the school, we have a network lab isolated from the main schools network. As a final project, my group is trying to add an internet access to a couple of the computers in the network.

The lab includes a batch of 10 computers all networked through a switch. I am bringing in my laptop which has a ethernet port and wireless network capability. I can access the internet through the wireless connection through the schools wireless access. So in essence, I'm connecting to the schools network and using the internet through it.

The setup is to hook my laptop to the switch and share the internet access that is coming through the wireless connection. I setup a workgroup which included a desktop and my laptop. They were able to see each other with no problem. I tried using the network wizard to do ICS. The internet worked on my laptop, the network worked fine, but I couldn't get the internet to work on the desktop.

Both computers are running Windows XP. The laptop has Home and the desktop has professional. Any help in solving this problem would be appreciated! Thanks!