The first way is to connect the PC directly to the TV. You usually do this via HDMI. Many modern computers have a HDMI port or you can use a DVI to HDMI adapter. Some TVs have a VGA port which you can use if your PC doesn't have a HDMI port. You can get a remote from ebay or other places. If you get a media center remote it will work without configuring any special software since it will use the built in Microsoft drivers.
The other method is to use an XBOX 360, connect it on the same network as the PC and use it as an extender. When used an as extender it will have most media center functions. You can get one of the XBOX media remotes and use it to control the XBOX. You're allowed to have up to 5 extenders with the regular Windows 7 license and it makes a pretty sweet whole home DVR solution. This is what I use.
The Echo, like the Xbox 360, is a Media Center extender, except without the gaming system. Hopefully they will be reasonably priced (well under $199) so they can be used to build economical whole house DVRs.