GetLogicalDrives issue

The problem there is that the DriveInfo class wasn't introduced until .NET 2.0.

If you're still using .NET 1.1, then you'll have to either use WMI (and the Win32_CDROMDrive class in particular) or call the Win32 API function GetDriveType()directly. The latter is easier and quicker:

     _
     Shared Function GetDriveType( ByVal lpRootPathName As String) As Integer
     End Function

     Const DRIVE_CDROM As Integer = 5

     Sub GetLogicalDrives()
        Dim returnValue As String()
        returnValue = Directory.GetLogicalDrives
        Try
            Dim drives As String()
            drives = System.IO.Directory.GetLogicalDrives()
            Dim str As String
            Dim driveType As Integer
            For Each str In drives
                driveType = GetDriveType(str)
                If driveType = DRIVE_CDROM Then
                   ComboBox_cd_drive.Items.Add(str)
                End If
            Next str
        Catch exp As System.IO.IOException
            System.Console.WriteLine("An I/O error occurs.")
        Catch exp As System.Security.SecurityException
            System.Console.WriteLine("The caller does not have the " + _
                                       "required permission.")
        End Try
    End Sub

Try this:

Sub GetLogicalDrives()
        Dim returnValue As String()
        returnValue = Directory.GetLogicalDrives
        Try
            Dim drives As String()
            drives = System.IO.Directory.GetLogicalDrives()
            Dim str As String
            Dim di As System.IO.DriveInfo
            For Each str In drives
                di = New DriveInfo(str)
                If di.DriveType = DriveType.CDRom Then
                   ComboBox_cd_drive.Items.Add(str)
                End If
            Next str
        Catch exp As System.IO.IOException
            System.Console.WriteLine("An I/O error occurs.")
        Catch exp As System.Security.SecurityException
            System.Console.WriteLine("The caller does not have the " + _
                                       "required permission.")
        End Try
 End Sub

Incidentally, I changed the Function to a Sub as you weren't actually returning anything - just listing the drives in the ComboBox.