Where can I buy a DVD writer?

[soundfx4]

Hi, I would like to buy a DVD writer because of X-box. (not like microsoft will get hurt if we burn there games) But I don't know where to buy one? I don't want to buy one just yet because of the price, but when the price comes down, I would like to know where I will be able to get one. Also, how big are DVD disk? I mean the blank ones you can buy. I saw that they were like 3-5 gigs, and usualy DVD movies are 10-20 gigs. Is that all right? If so then they must be doing that so people can't rip and copy DVD movies so easily. Please let me know, thanks