5.25-inch external drive bays can hold several different types of hardware. A CD burner, like the one shown above, is just one example. CD-R disks can store around 700MBs, (or 700,000,000 bytes), of information. A CD-R drive can read and write information, but it cannot erase it. A CD-RW drive can also read and write data, but it can also erase the data and rewrite new data, which is useful if you save something and later wish to remove it. CD-RW drives can use both CD-R disks and CD-RW disks. The recording speed rating associated with CD-R drives varies up to 54x. It varies up to 32x for CD-RW drives.