Aqui teneis un sencillo codigo para ejecutar captura del escritorio (PrintScreen) o solo del area del formulario que tenga el foco (Alt + PrintScreen):

Código:
Option Explicit

Private Const VK_MENU = &H12
Private Const VK_SNAPSHOT = &H2C
Private Const KEYEVENTF_KEYUP = &H2

Private Declare Function MapVirtualKey Lib "user32" Alias "MapVirtualKeyA" (ByVal wCode As Long, ByVal wMapType As Long) As Long
Private Declare Sub keybd_event Lib "user32" (ByVal bVk As Byte, ByVal bScan As Byte, ByVal dwFlags As Long, ByVal dwExtraInfo As Long)

Private Sub Command1_Click()
 ' Captura toda la pantalla o area del escritorio:
 Call keybd_event(VK_SNAPSHOT, 0, 0, 0)

End Sub

Private Sub Command2_Click()
 ' Captura solo area del formulario que actualmente tiene el foco:
 Call keybd_event(VK_SNAPSHOT, 1, 0, 0)

End Sub
Luego, podeis utilizar el objeto Clipboard de VB 6.0 para 'pegar' la captura en un control grafico como un PictureBox:
Código:
Set Picture1.Picture = Clipboard.GetData(vbCFBitmap)
Salu2...