'colores y resolucion
Private Declare Function GetDeviceCaps Lib "gdi32" (ByVal hdc As Long, ByVal nIndex As Long) As Long

Private Type tResol
    Width As Long
    Height As Long
    Bits As Integer
End Type
Private Disponibles() As tResol

Private Declare Function EnumDisplaySettings Lib "user32" Alias "EnumDisplaySettingsA" (ByVal lpszDeviceName As Long, ByVal iModeNum As Long, lpDevMode As Any) As Boolean

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

Const CCDEVICENAME = 32
Const CCFORMNAME = 32
'Las declaraciones de estas constantes están en: Wingdi.h
Const DM_BITSPERPEL = &H40000
Const DM_PELSWIDTH = &H80000
Const DM_PELSHEIGHT = &H100000

Private 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
Dim DevM As DEVMODE


en el load 
'para saber la resolucion de la pantalla y hacer la recomendacion
Dim Mensaje As String
Dim Col, bit, largo, alto As Integer
Col = GetDeviceCaps(frmMainMenu.hdc, 12)
largo = GetDeviceCaps(frmMainMenu.hdc, 8)
alto = GetDeviceCaps(frmMainMenu.hdc, 10)

   'Mostrar las resoluciones disponibles
    Dim A As Boolean
    Dim i As Long
    i = 0
    Do
        A = EnumDisplaySettings(0&, i&, DevM)
        i = i + 1
        If A Then
            ReDim Preserve Disponibles(i - 1)
            With Disponibles(i - 1)
                .Width = DevM.dmPelsWidth
                .Height = DevM.dmPelsHeight
                .Bits = DevM.dmBitsPerPel
            End With
        End If
    Loop While A

If largo > 800 Or alto > 600 Then  'cambiar resolocion automaticamente
    If AdoOption.Recordset.Fields("Cambiar_Resolucion_800X600_opt") = True Then
        Call cmdCambiarResolucion_Click
        Exit Sub
    End If
    
End If

Private Sub cmdCambiarResolucion_Click()
'Exit Sub
    'Cambiar a la resolución indicada
    Dim i As Long
    'Si sólo se quiere cambiar la resolución,
    'manteniendo los colores:
    DevM.dmFields = DM_PELSWIDTH Or DM_PELSHEIGHT
        DevM.dmPelsWidth = 800
        DevM.dmPelsHeight = 600
        DevM.dmBitsPerPel = 24
    Call ChangeDisplaySettings(DevM, 0)

End Sub