My main computer is a notebook running Windows 7. The notebook connects to a docking station via USB 2. The docking station has a wired, Fast Ethernet connection (100 Mbit/s). Additionally I have a Wireless G WiFi connection (54 MBit/s). Finally, I have an Ethernet cable that provides a Gigabit Ethernet connection (1 Gbit/s) which I usually don't bother to connect, because the docking station's Fast Ethernet connection is fast enough most of the time.

However, when I backup my NAS drive, I need the fastest network connection available, so I plug in the Gigabit Ethernet cable. After noticing that the backups were running slower than expected, I opened the Windows Task Manager and selected the Network tab. I was surprised to find that the docking station's Fast Ethernet connection was being used, instead of the much faster Gigabit connection.

Windows 7 is supposed to give priority to the fastest network connection, but sometimes it gets it wrong, as happened to me. Here's how to fix this issue:

1. Go to the Network and Sharing Center (Control Panel / Network and Internet / Network and Sharing Center).
2. Click the "Change adapter settings" link.
3. For each network connection, right-click the connection and select Properties
4. Click Internet Protocol Version 4 (TCP/IPv4) (or v6 if you're on IPv6).
5. Click Properties, then click Advanced...
6. Make sure the Automatic metric checkbox is cleared.
7. Enter a unique number, inversely proportional to the connection's speed, in the Interface metric textbox. In other words, enter 1 for your fastest connection, 2 for your next fastest connection, and so on.

Now go to the Windows Task Manager's Network tab and verify that Windows 7 is using your fastest connection in preference to the slower ones: