Use the nokia OVI suite. When you drag the video into the phone and if the format is not playable, there will be a dialog box asking if you want to convert video. Just click ok and it will automatically transcode and transfer to you phone. Nokia s60v5 phone will support 3gp, mp4, rm and wmv and avi, mkv through core codec (Although I think the player does not support s60v5 yet). Please note that not all resolution is supported and obviously the phone will not have the power to play HD movie.