My advise is to buy a new Media Center PC.
A Media Center PC has a built in TV tuner card and DVR capabilities (so you could record TV shows/movies onto your hard drive).
If you have Antenna/Cable TV - you just hook up the coax cable to the input to any Media Center PC and you have everything you want - just like hooking it up to your regular TV.
However (!) Satellite TV (Dish, DirectTV, Vios, etc...) needs special software/box to help the TV tuner card "read" the incoming signal.
Anyone with experience knows that you could hook up an Antenna/Cable directly to your TV and get signal, no problem - but you can't hook a satellite directly to a TV without having a box/decoding software to be able to view channels on a basic TV and the same is the case for a Media Center PC as they have the same type of input signal chip.
The Media Center PC is definitely the best bang for your buck, in my opinion.
Check out these sites to watch streaming TV shows (that don't have to downloaded to your hard drive)
http://www.veoh.com/
http://sharetv.org/
http://66stage.com/
there are SOOO many sites that offer TV viewing. Google search and you'll find hundreds of others!
But (!) *Winks* LOL - Here's a link that will let you watch new movies that are in the theaters (right now) on you PC. For free! :D
Go here:
http://www.watch-movies.net/
I hope this info helps. Good luck on your purchase! :D