The Slingbox is the device you need in order to stream the TV signal out to a computer. You only need to connect the Slingbox next to your set top box. Then, connect the Slingbox to your router. On your PC, you only need to either download and install the SlingPlayer software or visit www.slingbox.com in order to use the web-based application.
The following link will provide you with the general information about the Slingbox PRO HD.
If your PC is located on a different room, you can also check some information about the SlingLinks.
Finally, you must also know that none of the Slingbox models are compatible with the HDMI cable.