Every time I try to do this is screws up the modem and I have to reboot it.
>I know it can be >done because I've seen it but I am apparently doing
>something wrong. They had it at work, two >NICs in the master PC in the
>office then that fed a router and thus all the other PCs in the >shop.
No-one uses a Windows PC for Internet Connection Sharing any more.
Connect a suitable wireless router directly to the modem and configure the router correctly.
The rest of the network can use wires, switches and additional wireless access points as necessary.
Old Guy