Drive bays are where the computer's drives are installed. CD-ROM and DVD-ROM drives can only play disks. CD R/RW and DVD R/RW drives can both play and record to disks. These drives are normally called "burners." You can erase and record again with RW disks, but R disks will only allow you to record one time. Hard drives have larger storage areas than the other drives. Their disks are sealed and cannot be removed. The hard drive is where the computer's operating system, (like Windows XP), is kept. Sometimes people confuse the hard drive with memory, but the hard drive does not have anything to do with memory. It is for storage only. Floppy drives do not hold very much information, but they are handy to use for smaller files. Zip drives and tape drives are good to use for backing up a lot of files. Drives with removable disks are handy for taking files to other computers.