I could have sworn that Vista had one built in, however it may be that basic doesn't include it... regardless, anything that says dvd decoder should work.  Just make sure it says dvd decoder or plays commercial dvds, stuff like that.

Welcome to the forums :emotion-21:

Try using VLC Media Player (which is FREE) :emotion-55:

It includes a large number of popular encoding and decoding codecs :emotion-5:

When I look on the Dell website and go to dvd decoder I can't tell which one I need to download.

I'm fairly sure that Dell uses PowerDVD as its DVD decoder.  You should've received a CD or DVD with PowerDVD on it along with your Dell system.  Just pop that into your system and follow the instructions.