Disk Drive (ComputerCraft) contains information about the ComputerCraft mod.
The Disk Drive can be placed adjacent to any side of a Computer for it to be recognized by that Computer. The disk drive enables you removable storage to transfer your programs between Computers. You need a Floppy Disk to write data onto.
Another use for the Disk Drive is to put music disks from vanilla minecraft and run the "dj" application on the Computer without requiring a Jukebox that uses up one diamond to make. However, a disk drive uses very little resources to create.