Windows 7' Media Center is more than enough for simple organizing. You could boost it with commercial or free DLNA servers (I am using TVersity at home), or replace Windows with media-oriented Linux distro (MythTV comes into mind).
As for your TV - to connect wirelessly, you can get a "Smart TV" with DLNA support, or Roku-type device for streaming. If you wamt wireless monitor (that is, to show e.g. your gaming on the TV), things are muich more complicated (and expensive).