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Drive-naming secrets

Drive-naming secrets
By Scott Mueller

Here's something that most people, whether they're computer-savvy or not, wonder about. How does Windows decide which drives are which? This tip, excerpted from InformIT, tells what happens, and what you can do about it.

The basic rule is that devices supported by ROM BIOS-based drivers come first, and those assigned by disk-loaded drivers come second. Because floppy drives and hard drives are normally ROM BIOS supported, these would come first, before any other removable drives.

The system therefore assigns the drive letter A to the first physical floppy drive. If a second physical floppy drive is present, it is assigned drive letter B. If there is no second floppy drive, the system automatically reserves B: as a logical drive representation of the same physical drive A:. This allows files to be copied from one disk to another by specifying COPY file.ext A: B:.

The system then checks for installed hard drives and begins by assigning C: to the master partition on the first drive. If you have only one hard disk, any extended partitions on that drive are read, and any volumes in them are assigned consecutive letters after C:. For example, if you have a hard disk with a primary partition as C: and an extended partition divided into two logical volumes, they will be assigned D: and E:.

After the hard drive partitions and logical volumes are assigned, the system begins assigning letters to devices that are driver controlled such as CD-ROM drives, PCMCIA-attached devices, parallel port devices, SCSI devices, and so on.

Here is how it works with only one hard drive split into three volumes, and a CD-ROM drive:

One Primary Partition C:
One Drive Extended Partition 1st Volume D:
One Drive Extended Partition 2nd Volume E:
CD-ROM Drive F:

When a removable drive is added to this mix, it is assigned either F: or G: depending on the driver and when it is loaded. If the CD-ROM driver is loaded first, the removable drive is G:. If the removable drive driver is loaded first, it becomes F: and the CD-ROM drive is bumped to G:. In DOS, you control the driver load order by rearranging the DEVICE= statements in the CONFIG.SYS file. This doesn't work in Windows because Windows 9x, Millennium, NT, and 2000 use 32-bit drivers, which aren't loaded via CONFIG.SYS.

You can exert control over the drive letters in Windows by manually assigning drive letters to the CD-ROM or removable drives. You do this as follows:

  • Right-click My Computer, and choose Properties.
  • Choose the Device Manager tab.
  • Click the + next to the CD-ROM drive icon. Right-click the CD-ROM drive, choose Properties, and select the Settings tab.
  • Select and change the Start Drive Letter.
  • Select the same letter for End Drive Letter.
  • Click OK and allow your system to reboot for changes to take effect.
  • Repeat the previous steps by clicking the + next to Disk Drives and assign a different drive letter to your removable drive.

Using these steps you can interchange the removable drive with the CD-ROM drive, but you cannot set either type to a drive letter below any of your existing floppy or hard drives.

To read more of this tip, click over to InformIT{3F073F8E-5057-42A2-942D-0E36BD4C66B6}. You have to register to read the tip, but registration is free.

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