VLC Media Player
Supported OS: Windows7/Vista/XP
VLC Media Player is a popular and free cross-platform multimedia player
VLC plays most multimedia files as well as DVD, Audio CD, VCD and many popular video files such as MPEG-2, DivX, H.264, MKV, WebM, WMV and many more with no codec packs needed.
Safe and Secure: 
VLC media player is a highly portable multimedia player for various audio and video formats as well as DVDs, VCDs, and various video formats without external codec or program.
It can also be used as a video server in unicast or multicast in IPv4 or IPv6 on a high-bandwidth network.
VLC can play:
- MPEG-1, MPEG-2 and MPEG-4 / DivX, MKV files from a hard disk, a CD-ROM drive, and so on
- DVDs, VCDs, and Audio CDs
- From satellite cards (DVB-S)
- Supports several types of network protocols: UDP/RTP Unicast, UDP/RTP Multicast, HTTP, RTSP, MMS, etc.
The program and its source can be downloaded for free directly from here.