I have a 1 Gbit per second connection, but every time I download something of the internet (for example Steam games), it will only allow 100 Mbits per second and everytime the speed reaches 100 Mbps the network graph in Task manager shows 100% receive connection limit and the PCs starts to lag and becomes really slow. But when my friend tries to download something of the internet on his PC via the same cable. He gets up to 800 Mbps. I have installed the newest Ethernet driver (Realtek LAN Driver for Microsoft Windows 8 (32-bit, 64-bit)).
niklamacz: The Ethernet adapter on your laptop is probably built into the motherboard, so it cannot be changed out for a replacement. However, you can use a USB adapter, like allennnn suggested above, or possibly an Expresscard/PC Card if your laptop has a slot for it.
To allennnn: I know! If the 6-year old Dell I am currently typing on has a 10/100/1000 Mbps Ethernet port on it, why can't newer ones? Seems like it is only the business-class laptops that have Gigabit Ethernet.