Windows and DOS use a system of letters to identify the different drives that are fitted to the PC. A PC can have up to 26 drives fitted - one for each letter of the alphabet. Each drive is normally given a drive letter, for example the hard disk is normally drive C. This is usually written as C:. The standard configuration is drive A: is a floppy disk drive, drive B: a second floppy disk drive, C: is the hard disk drive, and D: is a CD-ROM drive. 


If you are connected to an office network, you might have other drive letters that actually map to a disk drive on someone else's PC. Lastly, if you have a very big hard disk drive, it might have been partitioned when you bought the PC. This means that the drive has been split up into manageable sections, called partitions. For example, if you have a hard disk drive with a 500Mb capacity, you might find it more useful to split it up into two sections, each 250Mb in size. In this case, the first would be referred to as drive C: and the second as drive D:. If you added a CD-ROM drive to this PC, it would now be called drive E:.