Network Sharing / Homegroup on private LAN

Hi, I have searched but not found much with what I want to set up. I currently have a wireless connection to the internet for my PC and Laptop. What I would like to do is setup a private LAN with an old router to use but be able to keep the desktop connected to both WiFi and this LAN.

The only way I have managed to do so so far is by manually setting the IP address for the LAN (disable DHCP, change IP address etc) and assigning the LAN IP address manually to my desktop/laptop, leaving the gateway fields blank. I have noticed that doing this makes my network "Unknown" to Windows 7, which then forces it into Public mode, and disables Homegroup.

Is there a way for me to accomplish what I want?


Is pretty much how I want it to work. The desktop has two NICs, the laptop does not, so I realize the laptop would be a one-or-the-other scenario.

Well first off one router is old enough that it doesn't have wifi built in, which is the one I want to use for my private LAN. Secondly, I do not want the private LAN (Router B) to have access to the outside world at all, I'd prefer it be it's own system, not connected into the wifi (Router A) setup.