WinMEnc is the free Windows GUI of mencoder. It can encode from any media formats (AVI, VCD, DVD, rm/rmvb, MP4, etc) to the AVI file with the format of MPEG1/MPEG2/DivX/Xvid/H264, etc.
Depend on your CPU, download one set of mplayer/mencoder binary file from the below link and extract it to the same directory. http://oss.netfarm.it/mplayer-win32.php