Not able to see mpeg4 video

I lost cd tat came wit my player and so i was not able to use Arcsoft to convert videos. i made use of "4u MP4" video converter and converted the avi to mpeg 320x240 video:512fps audio:128fps.... But only the .avi files are visible in my player and the converted mp4 files are not visible.. wen tried playin .avi files it says "does not support" .. Folks please provide me a solution am trying really hard to watch a video from day 1 but havent succeded :( .... plz provide the name of converter to use and the exact format that the player accepts... where should i place the video file in my player "videos" folder is not visible in "my computer" ..!! waiting for ur expert advice ... thanks in advance