problem downloading videos. MP4's and MOV's files
 

anytime some video finishes the download and i try to watch it, it takes a couple of minutes to come up and then i get a message saying that is unable to play the file because is a file that quicktime does not support. and i only try to download mp4's and mov's format in order to be played on my ipod. PLEASE HELP ANYBODY

Try installing the VLC media player, it has all the codecs pre-installed and can play just about all files...
VLC media player - Overview

Get one of these pacs also...
For XP this codec pac is very good
Download XP Codec Pack 2.0.8 - XP Codec Pack is one of the most complete codec pack
Or for Vista this pac
Vista Codec Package v4.4.7 Beta 4a (freeware)