Can someone guide me on how to connect DirecTV to my desktop computer so that I can watch from my computer and also use it as a DVR?

I currently have four lines from coming from the dish, 1 is connected to an HD DVR receiver, 2 is connected to a normal receiver, and the 4th is not connected to any receiver. The 4th line is the line I would like to use for this purpose.

Thanks in advance!

You will need to connect the line from the dish to a receiver, as you cannot (legally) decrypt the satellite signals without piping it in through a satellite receiver. If you use a satellite receiver and something called an "IR blaster" you can control the receiver from your computer and still gain the benefit. Some TV capture cards online have this function built in and include the remote, so look for some good deals online. Newegg or Tiger Direct would be my choices.

Thanks Indigo. I will be picking up the Hauppauge HVR 1600 HD Tuner with IR receiver remote. Hopefully it will workout.