If you're using VB4 32 bit, you can use the GetLogicalDrives API to get a 32-bit bitmask of all valid drive letters. FOr example, bit 0 is drive A. If it's a 1, then there is drive A in the system. Then use GetDriveType(""A:"") and check the return. if the drive is a CD-ROM, you will get a return of DRIVE_CDROM.

Dim dwDrives As Long
Dim i        As Integer
Dim Mask     As Long

  dwDrives = GetLogicalDrives()  
  Mask = 1  
  For i = 0 To 26  
    If (dwDrives And Mask) Then
      If (GetDriveType(Chr(65 + i) & "":"") = DRIVE_CDROM) Then 
         ' This drive is a CD-ROM
      End If
    End If
    Mask = Mask * 2
  Next i