I downloaded a video from mega upload, and it wasnt in mp4 format so I downloaded several converters one after another to try to convert it. I tried leowa even! It said that it was in mp4 format, and it looked lke it did, and then I dragged the video onto itunes and it was there. So when I synced it onto my ipod it either said that ”this video wasnt added because i cant be played onto the ipod” or it would be on the ipod under movies and when i pressed on the video it would say that i needed to connct a video accesory (the screen would be a ”TV Out Enable”) Also, sometimes when i would dragg some videos onto itunes, it wouldnt add. I have a ipod nano 4th generation. (4th or 5th)

You need to convert your videos to iPod compatible format. Try this iPod converter: http://use4video.com/apple_IPod_converteā¦
What you can use is a Mp4 video converter or a professional ipod video converter.
i have used an ipod video converter for my ipod touch for weeks,this one is easy to handle and easy to use.you can have a look at this page for further information,
You have to first have the videos saved on your computer in its own folder. ( I prefer saving it on your desktop) after that, right click the video and it should give you many options. After that, select the option: open with, open with iTunes. From there, the video would be in your iTunes library. Hope this helped!