Delete or forget the old network and try again. As to drop out, that's OK with WiFi since it's an open system that simple things like an old cordless phone can bump your connection off.
I'd have more advice but details are too slim.
Recently, my PC has stopped automatically signing into my router at start up. It is also dropping out of the network periodically. I use a home wireless network, and am on Win 8.1 OS.
Any advice greatly appreciated.