DVD Burner
From The Big Bang Theory Wiki
A DVD Burner is a device for computers that allows one to burn files to a blank DVD, usually DVD-R or DVD-RW. They are very useful for backing-up large amounts of data. With an average capacity of 5 gigabytes per disc, they hold far more than blank CDs (CD-R, CD-RW) could hold.
Leonard is, according to Sheldon in The Peanut Reaction, in need of a DVD burner. He is presumably still in need of one as Sheldon opted to buy him a wireless router instead.
