Normally it's as simple as buying a computer and TV tuner card, but there's a catch in your case.
The power grid in Afghanistan probably doesn't run on the same 110-120V as the grid in the States does. It's probably using a 220-240V grid. So if you bought a computer over there, you'd need to get power adapters to be able to use it here.
The other problem is with the TV signal. The US, Canada, and Japan use a format called NTSC, while almost the entire rest of the world uses a format called PAL. NTSC TVs cannot use PAL signals and vise versa. Oncoming HDTV promises to unify this, but that doesn't do you a lot of good now. So you would either have to buy a TV tuner card that can handle both sets of signals, which would cost more, or get a new card when you get back here.
It would probably be better to get a physical TV set, and then an adapter box for it. Something that will convert PAL to NTSC or NTSC to PAL.
Ultimately, depending on how long you were going to be over there, I might just hold off until you get back. Then you don't have to worry about these details.
Greetings from here I have been here for a year and look forward to returning home, but I need help I am considering investing in computer and tv except me and tech are not very good friends how can i use a computor to watch tv and play halo or will these be able to run. I have other questions but maybe general info would be a good start , this is the second attempt to do this so some where ''out there'' are these same q's.