I have 2 laptops. Laptop A connects at house A but not B. Laptop B connects at house B but not at house A.

If your using wifi you have been setting up and saving the connections as default. you can just add the new wifi connections instead of changing your default connections.

when you search for the connection just add the new one's and when you go back from either house A, B or C you would still be able to see the wifi connection and just connect to it.

you may want to choose automatic on your internet/lan connection setup so you do not have to setup the IP address everytime.

confident, use a router. in the experience that your desktops are going to be in distinctive factors/rooms, going with a prompt router is possibly the final wager except you prefer to be tripping over cables =) in case you employ prompt router, you're able to get the two machines a prompt adapter. There are USB ones available that value below $20 a chunk or perhaps $10 a chunk while on sale (ie, from fry's). Your bf's mom's device could be plugged promptly into the router so she doens't want an adapter... happy to help in case you want extra information.