how to connect laptop to tv

hi,

i just visited a relative's house a couple of days ago and among other things showed them a collection of video programs i have. most of them are downloaded stuff not real vcd/dvds. they would like to see them, but on the big tv.

so i tried to connect the laptop to the tv with a video cable but the pictures wont transfer. is there something i am doing wrong? do i have to enable anything in the laptop without which the pictures/screen wont be transferred to the tv?

please let me know if you are familiar with this problem and its solution.