Question:
I would like to know how to call the CD-Rom, or rather search for its drive letter.

Answer:
You can use the FileSystemObject (Microsoft Scripting Runtime in the references dialog). Iterate through the Drives collection of the FileSystemObject and check its DriveType property and DriveLetter property. DriveType 4 is the CD ROM.

Set a reference to the Microsoft Scripting Runtime and try this code.

Dim objFso As New FileSystemObjectDim objDrive As DriveFor Each objDrive In objFso.Drives    With objDrive        If .DriveType = CDRom Then            MsgBox "CD ROM is " & .DriveLetter        End If    End WithNext objDrive