Please check the below to the files are compatible with COWON V5. * Video Format - AVI, WMV, ASF, MP4, MKV, MPG/MPEG, DAT, TS, TP, TRP, M2TS, 3GP * Video Codec - XviD, H.264(MPEG4-AVC), WMV9/8/7, MPEG1 * Video resolution - up to 1280x720, 30fps * Audio Codec - MPEG1 Layer 1/2/3, AC3, WMA, OGG Vorbis, PCM, FLAC * Audio resolution ? up to 48KHz, 320Kbps * Subtitle - SMI, SRT Please check the file information with COWON Media Center- JetAudio. If your file is not playing on COWON V5 even though your file is encoded with those specifications, your file might be damaged. Please convert the file again by using COWON Media Center, JetAudio for use in COWON V5 .