Well if you have an old laptop that has a VGA or DVI output, you can use that instead of another device (bluray player/game console/etc) to connect the TV to the network. If your TV doesn't have a VGA or DVI connector -- and it probably does -- you would need a VGA to HDMI adapter. You also need a $2 3.5mm to 3.5mm 6 foot RCA cable to get the sound to the TV. I used a VGA and 3.5mm RCA cable with an old laptop for a while before I built a HTPC to play bluray images from a server, and stream Netflix, to one of my older TVs.
You are basically just using the TV as your laptop monitor, which you set up in the display control panel. The laptop connects to the wireless or wired network. Then you can use the Netflix PC app to play Netflix, or you can play avi files with Windows Media Player or some other program.