Need High quality videos!

Ok...I've downloaded videos from youtube, i converted them from flash video to MPG or MPEG....But everytime i watch them they're all blocky and random pixels are laggy...I've just RECENTLY discovered that it get's like this when i convert them from a flash video to an MPG format...I use Riva FLV Encoder and i was wondering how i can convert them and still have in high quality?

 

had the same problem myself mate ,
at the moment im using a programme called super converter which converts most video formats i know of and is dead simple to use heres a link to it

http://majorgeeks.com/Super_d5117.html

and a link to the authors site for more info on it

http://www.erightsoft.com/SUPER.html

hope it helps