The DHCP server for the Internet Connection Sharing (ICS) feature in Windows uses the IP address of 192.168.0.1. As you may know too well, this is the default address of many routers. Since each device on the network must have a unique IP, there’s a conflict when the local network used to provide the Internet access for ICS has a router with the same IP. You can change the router’s IP, or change to different subnet altogether.
However, you can also change the IP used by ICS in Windows Vista by making registry changes to the ScopeAddress and ScopeAddressBackup keys, in three different places: