uploaded videos are not appearing in my code base

i uploaded some video files like a.wmv,first.flv through add video link. and installed flash player and jw_flv_player and put them in foledr videos..

1) when playing it it shows

" Your browser is not able to display this multimedia content.
Problems viewing videos?
Download latest Flash Player "

2) After some time the files are missing in the directory video/

"when accesing them it shows file not available at specified loaction."