Another choice is what interface you want. CD-ROM drives come in IDE , SCSI , or other proprietary interfaces, such as that of Creative's original multimedia kit. Most drives are IDE, and that is the easiest type to install. You have to decide, before buying, how you want to put the disk in the drive. CD drives come in three forms here.
Some drives use caddies to hold the disks.
You put the CD in a caddie then stick the caddie into the drive itself. The caddie helps to stabilize the disk, as well as protect the disk. Another kind of drive is one with the slide out drawer. When you press eject, the drawer pops open and you lay the disk in there. This is much like an audio CD player.