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:
iperf -c 126.96.36.199
You may need to use larger packet sizes to get the full speed, try adding
-l 64K -w 64K or something.
If you want to try online, Visit http://www.speedtest.net/
Here you will find the detail of your LAN bandwidth along with downloading and uploading speed. Downloading Speed is your actual speed.