Stream video from computer to TV

Here's the situation.I am a recent resident at an assisted living facility. Because I have some experience with PC's I was asked to maintain the facility resident computer, a PC with W7.
The computer is in the back of the media room, a 50 inch TV is in the front of the room. Also in the front is a modem and router. The computer is wireless and gets on the internet wirelessly through the router. The room is about 45 feet long.
I would like to play video from the computer to the TV. I don't know how. I know it can be done. I am open to suggestions and would like t keep it cheap. The facility is in a corporation and it is difficult to get money.

What kind of TV is it?

It's a Sanyo. I need help to get to the model number. I am confined to a wheelchair.

Get yourself a used PS3 to use as your media server. Prolly get one at a pawn shop or 2nd hand somewhere for a fraction of the retail price of a new one. Since you only want to use it as a media server it doesn't matter if the CD drive in the PS3 works or not. I'm using a PS3 with a broken cd drive as a media server and it works great cause the kids can't put any games into it.
I used a program called "PS3 Media Server" for the longest time to watch movies and TV I downloaded until I got a Netgear R6300 router that has a media server built in but still use the PS3 as the renderer.
PS3 Media Server
Watching movies on our 52" plasma is awesome and heck of alot better than before when we watched on the computer monitor.
Also I found out that wireless isn't all that great for streaming video so I've hardwired my PS3 in and have had no problems with streaming video at all. Your not using any internet either while streaming since your within a home network all your using is the ethernet cable from router to PS3 console.