Windows 7's Ad-hoc network facility is designed for "one off" applications and is not designed to be repeatable. It is designed to be used for temporary connection of two PCs for file sharing. It is designed to be used once only
If you require a network between two systems on a permanent basis then this needs to be set-up as a regular network. you will need to configure the IP addresses manually as you will not have a router which would normally supply DHCP, DNS etc.