I have an Intel DG31PR motherboard. Recently installed a Gigabit router, but Win 7 Device Manager shows the Realtek PCIe GBE Family Controller Network Adapter running at 100 MB. How can I force it up to Gigabit? Other devices on the wired network are running at Gigabit speed.
I can't think why the adapter would negotiate a 100 connection unless maybe you are using an old piece of ethernet cable. Try using Cat5e or better. Also assuming you've installed the Realtek LAN driver available for download from the intel website.
right click and get properties for the adapter
under the advanced tab there's a property setting called Speed & Duplex. By default the value is set to Auto Negotiation. Set the value to 1.0 Gbps Full Duplex.