How do you change drive letters?

Because these letters are used directly by normal applications (unlike the /dev/* names in Unix-like operating systems), the addition of an additional hard drive can be disruptive to applications, which then require reconfiguration or even reinstallation. This is especially true if there are logical drives in an extended partition on the original hard drive and the new hard drive has a primary partition, as it would then cause the logical drives on the first hard drive to change letters. However, even if the new hard drive had only logical drives in an extended partition it would still disrupt the letters of RAM disks and CD-ROM drives. This disruptive system persisted through the 9x versions of Windows but NT adopts a slightly different system. It uses the traditional rules when first installing but after that it tries to preserve the letters of existing drives until you change it.