Well you can download K-Lite Mega Codec Pack from here(full):
*rapidshare.com/files/33642162/klmcodec210.exe
It plays EVERY Video Format e.g. MPEG-4, DIVX, XVID, MKV, 3gp, RMVB, MOV ,etc
To Encode Your Windows I recommend Total Video Converter:
*www.effectmatrix.com/total-video-converter/tvc.exe
It can convert ALMOST ANY video format to ANY video format e.g. 3gp to divx, divx to mpg etc. given that you have the codecs!!!!
Further, H.264 is a video compression standard for MPEG-4.