Sylvania Mp3 Video Player Format error?

Okay I just got a gift, a Sylvania Mp3/Video player, Music works fine but Videos do not, It tells me there is a Video format error. I did what I read in the manual paper, Convert video to .Avi set resolution to 320×240 but didn’t do anything, I even used the convertung software the product supplied.

Perhaps its a computer problem, I can not play the Converted videos on my computer, I can but no audio because I am missing Mp3 – Media layer 3 or whatever Codec.

If you think it can be solved by the codec, can you please give me a link?