How to Install a DVD Decoder for Windows XP
If you want to watch a DVD within Windows XP, you will need a DVD decoder. A DVD decoder or codec as it's sometimes called, unscrambles the video and allows it to be played through software. In Windows XP, there is no built in software for this, so you will need to install a third party piece of software to watch movies on your computer.
Put a DVD in your drive and try to play it. You may already have a DVD decoder that will play DVDs on your computer.
Install DVD player software. Most DVD drives come with free or OEM DVD player software. Install this software, and you can watch DVDs through the software, using the built in DVD decoder. Sometimes Windows Media player will see this DVD decoder and use it to play movies.
Open Windows Media Player and try to watch a DVD. If, after installing a DVD player program, Windows Media Player still won't play, it will ask you to find a codec. Point Media Player to the location of the executable program you just installed. An executable is the file that ends in .exe.
Go to Microsoft's website to find DVD decoder codecs. Microsoft has a list of decoders that you can buy and install. Once you buy these codecs, just click on the installation file and it will install and be ready for use in Windows Media Player.