Came accross this free converter that is ideal for the 5800's 640 * 360 screen. I have used it to convert the Dark Knight Batman movie and the results are excellent.
This is the site for the instructions :
http://www.techiechips.com/convert-movies-and-videos-nokia-5800/
This is the site for the converter download :
http://www.erightsoft.com/SUPER.html
Don't get confused and download the advertised Prismn converter Scroll down to the bottom of the page where it says " Start Downloading SUPER �" follow the links.
Hope you enjoy it as much as I have.
😊