How can I test the speed of a LAN? I hope there is something baked into Windows to do this, because I am unable to install any third-party products.
Well you can just look at the network in the control panel and see if the LAN is connected at 10/100/1000 mbit. But that doesn't tell you the whole story. If you want to test the speed between two PCs, you really need a tool to do it. One tool I've used that seems pretty good is 'iperf', it's just a commandline EXE, doesn't require any install. 'ping' will tell you the latency, but not the available bandwidth.
Example usage of iperf:
On one PC run it in 'server' mode:
On another PC run it in 'client' mode, and give it the IP of the first PC:
You may need to use larger packet sizes to get the full speed, try adding
You can right-click on the LAN connection and then Check the 'Status'. That will give you the link speed. You can also open a command prompt and run ping.exe to ping other computers on the network.