A big problem for many vb-programmers is how to change the screen resolution, also because in the Api-viewer the variable for EnumDisplaySettings and ChangeDisplaySettings is missing!

1. Code for the basic-module

Declare Function ChangeDisplaySettings Lib "user32" _
Alias "ChangeDisplaySettingsA" _
(lpDevMode As Any, ByVal dwFlags As Long) As Long

Declare Function ExitWindowsEx Lib "user32" _
(ByVal uFlags As Long, ByVal dwReserved As Long) As Long    

Public Const EWX_LOGOFF = 0
Public Const EWX_SHUTDOWN = 1
Public Const EWX_REBOOT = 2
Public Const EWX_FORCE = 4
Public Const CCDEVICENAME = 32
Public Const CCFORMNAME = 32
Public Const DM_BITSPERPEL = &H40000
Public Const DM_PELSWIDTH = &H80000
Public Const DM_PELSHEIGHT = &H100000
Public Const CDS_UPDATEREGISTRY = &H1
Public Const CDS_TEST = &H4
Public Const DISP_CHANGE_SUCCESSFUL = 0
Public Const DISP_CHANGE_RESTART = 1    

Type DEVMODE
    dmDeviceName As String * CCDEVICENAME
    dmSpecVersion As Integer
    dmDriverVersion As Integer
    dmSize As Integer
    dmDriverExtra As Integer
    dmFields As Long
    dmOrientation As Integer
    dmPaperSize As Integer
    dmPaperLength As Integer
    dmPaperWidth As Integer
    dmScale As Integer
    dmCopies As Integer
    dmDefaultSource As Integer
    dmPrintQuality As Integer
    dmColor As Integer
    dmDuplex As Integer
    dmYResolution As Integer
    dmTTOption As Integer
    dmCollate As Integer
    dmFormName As String * CCFORMNAME
    dmUnusedPadding As Integer
    dmBitsPerPel As Integer
    dmPelsWidth As Long
    dmPelsHeight As Long
    dmDisplayFlags As Long
    dmDisplayFrequency As Long
End Type    

Example

Changes the resolution to 640x480 with the current colordepth.

Dim DevM As DEVMODE
'Get the info into DevM
erg& = EnumDisplaySettings(0&, 0&, DevM)
'We don't change the colordepth, because a
'rebot will be necessary

DevM.dmFields = DM_PELSWIDTH Or DM_PELSHEIGHT 'Or DM_BITSPERPEL
DevM.dmPelsWidth = 640 'ScreenWidth
DevM.dmPelsHeight = 480 'ScreenHeight
'DevM.dmBitsPerPel = 32 (could be 8, 16, 32 or even 4)

'Now change the display and check if possible   

erg& = ChangeDisplaySettings(DevM, CDS_TEST)

'Check if succesfull   

Select Case erg&
Case DISP_CHANGE_RESTART
    an = MsgBox("You've to reboot", vbYesNo + vbSystemModal, "Info")
    If an = vbYes Then
        erg& = ExitWindowsEx(EWX_REBOOT, 0&)
    End If
Case DISP_CHANGE_SUCCESSFUL
    erg& = ChangeDisplaySettings(DevM, CDS_UPDATEREGISTRY)
    MsgBox "Everything's ok", vbOKOnly + vbSystemModal, "It worked!"
Case Else
    MsgBox "Mode not supported", vbOKOnly + vbSystemModal, "Error"
End Select   

End Sub