BSplayer is windows player for playing back avi, asf, wmv, and mpeg video files or any other file for which you have a codec. Freeware.

Despite its small size and resource usage this media player has everything you need! Freeware.

The best DVD player for PC! Trialware.

Really good media player, plays every format available. Freeware.

VLC (VideoLAN) is a multi-platform multimedia player. It can read DVDs, VCDs, MPEG, and DivX files and from a satellite card. It can also read a stream from a network sent by the VideoLAN Server or another source. The stream can be MPEG 2 TS in UDP or HTTP packets unicasted or multicasted on an IPv4 or IPv6 network.

Windows Media Player, I am sure you all know it! If you still use 9 this will update it to 10.

This is the second best DVD player, has some nice features.