networking problems

I have a desktop that coes thru a cable modem and wireless router, I have a laptop I use the wireless to connect to , that all works fine , I am trying to network them together to share files but every time I use the network wizard my laptop loses its internet connection and i have to do a restore to get it back. These computers have been networked before so I know its possible . the reason the network got changed was the laptop got a worm and the people from the support told me the only way to fix was to do a complete restore with recovery disc. both are using winxp .i have the network code and put it in the laptop but still loses connection