How to play DVD, MPEG2 in Windows/Mac/Linux?

Please note the source while copy: http://www.dvd-x-player.com/wp/?p=519

In Windows
In order to play a DVD in Windows, you need a DVD Player software, then insert the DVD in your DVD-ROM and click Play using any player like DVD X Player, BlazeDVD 5 or WinDVD.
To play MPEG2 with Windows Media Player you need a DVD Player software installed or a MPEG2 Codec.
To play a copied/ripped DVD from your HD you can use DVD X Player, choose to open a directory and select the VIDEO_TS folder. Or use WinDVD, just right click on the play window and choose Source DVD from folder and choose the VIDEO_TS folder.
To play a copied/ripped DVD from the HD with DVD X Player, just click on the open button and choose Open DVD File from the Hard Disk Drive and open the video_ts.ifo in the VIDEO_TS folder.

In Mac
Play DVDs with VLC Media Player(Free).

In Linux
Play DVDs with VLC Media Player or MPlayer.

Problems in playing DVD
Problems may occur when you want to player a DVD, like CSS code, region protection etc (in Windows try DVD X Player or BlazeDVD 5).

All in all, choose a right DVD player software may save you a lot of trouble and just enjoy the DVD fun.