* VB-CODE (1)
Tip 165: Locating CD-ROM Drives Installed on a Computer System

December 5, 1995

Abstract
In a Microsoft? Visual Basic? application, you may need to determine what
types of disk drives are installed on a computer system. This article
explains how to locate the CD-ROM drives that are installed.

Using the GetDriveType Function
Occasionally, in a Microsoft? Visual Basic? application you may need to
determine whether a specific disk drive is a CD-ROM, removable, fixed,
RAM, or network drive. You can easily make this distinction by using the
Microsoft Windows? application programming interface (API) GetDriveType
function.

The following Declare statement should be included in your project:

Private Declare Function GetDriveType Lib "kernel32" Alias "GetDriveTypeA"
   (ByVal nDrive As String) As Long

To use the GetDriveType function, you need to tell it the name of the
disk's root directory. This should be in the format "c:\". After you call
it, the GetDriveType function returns a value that indicates the type of
disk drive.

The value returned by the GetDriveType function may be one of the
following:

Value            Drive Type
0                Unknown media type
1                No such root directory exists
DRIVE_REMOVABLE  Drive can be removed
DRIVE_FIXED      Drive cannot be removed
DRIVE_REMOTE     Network disk drive
DRIVE_CDROM      CD-ROM disk drive
DRIVE_RAMDISK    RAM disk drive

As you know, all disk drives are identified by an alphabetic letter,
starting with the letter A. The ASCII value for the letter A is 65.
Because there are 26 possible disk drives, you can use a For-Next loop
to test each possible disk drive to determine whether it is a CD-ROM
disk drive.

Example Program
This program shows how to locate all CD-ROM disk drives installed on the
computer system.

 1. Create a new project in Visual Basic. Form1 is created by default.
 2. Add the following Declare statement to the General Declarations
    section of Form1 (note that the Declare statement must be typed
    as a single line of code):

Private Declare Function GetDriveType Lib "kernel32" Alias "GetDriveTypeA"
   (ByVal nDrive As String) As Long

 3. Add a Command Button control to Form1. Command1 is created by default.
 4. Add the following code to the Click event for Command1:

Private Sub Command1_Click()
    Text1.Text = FindCDROM
End Sub

 5. Add a Text Box control to form1. Text1 is created by default. Set its
    MultiLine property to True.
 6. Create a new function called FindCDROM. Add the following code to this
    function:

Function FindCDROM() As String
    Dim Drive As Integer
    Const DRIVE_CDROM = 5
    FindCDROM = "No CD_ROM Installed"
    For Drive = 65 To 90
        If GetDriveType(Chr(Drive) & ":\") = DRIVE_CDROM Then

            FindCDROM = "CD-ROM Drive " & Chr(Drive) & ":\"
            Exit For
        End If
    Next Drive
End Function

Run the example program by pressing F5. Click the Command Button control.
A list of all CD-ROM disk drives installed on the computer system appears
in the Text Box control.