Windows 7: WiFi network is not showing up on Windows 7

i just got a new router, my brother helped me set it up
this router creates 2 wifi network, one named A, the other one named B.
A is faster than B (i don't know why)
on my ipad or phone or any mobile devices, i see both networks
but on my windows 7 PC, i only see B (the slower one)
so where is A? i need this faster one, why does it show up on mobile devices but not on my Windows 7 PC?
when he set up the router, he said to me that the website (routerlogin.net - where you can set up your router, put password, etc) says "A is available for Mac and B is available for Windows PC". is this the reason?
but what about mobile devices, they can connect to both networks,
please help, thanks

Other than the router's setup software, routers typically don't care about the OS of the machines connecting to it. But they do require that connecting devices operate on the protocols that it supports. If network A is running 802.11n and network B is 802.11g, and your PC can only do 802.11g, you will only be able to see B. If your PC can do 802.11n then you would likely see both.

What's the make/model of your router?