Ethernet

Hi,
I have an Asus M5A78L-M-USB3 board.

I'm not sure how old it is, but probably older than I think.

Its got an AMD Phenom(tm) ll X6 1055T 2.80 GHz processor.

I have been having issues with the Ethernet failing, so now am using a wireless dongle. This is slow.

My PC (desktop) is a small size case, so all the cards need to have low profile back plates.

I am going to reinstall Windows 8, upgrade it to 8.1, then 10.

I have checked to see if there are updated drivers for my onboard network adaptor: Realtek PCIe GBE Family Controller - There aren't.

I am going to have to fit an separate one.

My board has slots like this:


My Question is:
what should I be looking for for running Windows 10, bearing in mind it has to fit my slots (PCIe2?)

Any suggestions? Links?

Thanks

ps - Why do some Ethernet Cards have more than 1 Ethernet port, and what would the second one be used for?

Ethernet