your PC is already doling out the IP addresses for the LAN. For a wireless laptop to connect you would need either a wireless router to take the place of the ICS set up on your PC, or a WAP to be connected to the switch.
My PC is connected through a wireless modem to internet. It is also connected to a switch and I shared its internet connection (using WinXP home and small office network wizard). So by now all computers connected to the switch can access the internet, also my laptop.
My issue is how to share the laptop's internet connection. My dad's laptop is connected to my laptop through a wireless connection. I want to share the laptop internet LAN connection for the wireless network, so then my dad would be able to connect to the internet through my laptop. But when I check "Allow other network users to connect through this computer's internet connection" under LAN connection of my laptop, I recieve an error saying "Internet connection sharing cannot be enabled. A LAN connection is already configured with the IP address that is required for automatic IP addressing".