Please dont laugh at me

I am totally new to Linux and have installed the live cd 1.22 onto my old (now un-windowsed) pc. The install has gone ok.
The video captured is corrupt. I tried the different presets, but still not got a true image. I have gone through the wiki etc and found that I need to modify the /etc/modprobe.conf file. But if I start from "Home" and go through "var" to "etc" all I can find is a folder called "modprobe.d" that is empty.
Where can I find the actual file I need to alter?
The card looks like a Pico 2000 card, with a BT878 on it.
Can anyone advise a keen learner please?
Thanks