I always use this Video Converter. It supports the mutual conversion between almost all video/audio formats, and HD videos.
Input Formats: MPG, MPEG, MPEG2, VOB, MP4, M4V, RM, RMVB, WMV, ASF, TS, MKV, AVI, 3GP, FLV, MPV, MOD, TOD, MP3, MP2, AAC, AC3, WAV, MID, MIDI, WMA, M4A, RA, RAM .
Output Formats: MP4, H.264, AVI, MP3, WMV, WMA, FLV, MKV, MPEG-1, MPEG-2, 3GP, 3GPP, VOB, DivX, Mov, RM, RMVB, M4A, AAC, WAV, OGG, RA.
It also can set video effect, set Deinterlacing, trim your video length, crop the play region, merge into one file, customize output settings.
For more informaion and free download from:
http://search.yahoo.com/search?p=tipard+video+converter&toggle=1&cop=mss&ei=UTF-8&fr=yfp-t-701
It is easy to operate. Just few clicks are OK.
Hope it useful for you.