How do I convert a computer LCD monitor to a tv screen ?

I saw this in a Reebok showroom. They had converted the same LCD monitor I have into a TV screen, They had attached a black rectangular box at the back with an on off switch . I don't want to know about TVTuner cards. I just want a way to give it input through AV wires or whatever you call it. (They yellow, red & white ones). Please tell me the cheapest way to do this in India.

i would recommend this one!!its a bit expensive but is worth it..try serching under this categoryu wil get stuff as cheap as Rs 700http://shopping.rediff.com/shop/productdisplay.jsp?External-TV-Tuner-Card-SSD-TV-722-For-TFT-Monitors-By-Techcom&prrfnbr=10258254&source=browse&frompg=Computer%20Accessories