If you will not be watching Blu-Ray (HD DVD) at all then you can use any processor and you can go with integrated video on the motherboard.
You will need a DVD-ROM drive to watch DVD movies.
If you are going to be downloading content to listen / watch then get a large hard drive. It's perferable to have two hard drives; one for the OS and a separate hard drive to store all your media file. An alternative is to have a single large drive and partition it. A 20GB partition should be enough for the operating system and the remainder will be for your media files.
Once you throw Blu-Ray into the mix, then your hardware requirements (and cost) will increase.