Try to choose at least an 8 speed DVD - equates to roughly 40 speed CDRom.
You will need either DVD software to play movies but the decoding uses a lot of processor power or a MPEG decoder.
Some Graphic card manufactures are now combining MPEG acceleration on ther cards - ATI spring to mind.
A DVD decoder will give the best performance/Quality image combination.
The all in wonder 128 pro from ATI looks like a good option.