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Optical Drives...
An optical drive is a drive that can read different types of disc formats such as Blu-Ray, DVD or CD. Blu-Ray is the newest and is currently the most expensive, however, a dual-layer Blu-Ray disc can hold 50GB where as a dual-layer DVD can only hold 9GB so people believe Blu-Ray is well worth the expense. If you want a Blu-Ray optical drive then make sure you have a good, HD grahics card and a HD monitor. Also make sure that the graphics card is connected to the monitor using DVI or HDMI to be able to see true high-definition picture. You can get a DVD optical drive for around £15 or a Blu-Ray drive for around £50. 
Sources: General Knowledge, WikiPedia. The image of the optical drive was taken by one of our team members.