VB Code:
  1. Private Declare Function GetSystemMetrics Lib "user32.dll" (ByVal nIndex As Long) As Long

  2.  
  3. Private Sub Form_Load()

  4.  
  5.     Dim x As Long

  6.  
  7.     x = GetSystemMetrics(19)

  8.  
  9.     If x Then

  10.  
  11.         MsgBox "Mouse is installed"

  12.  
  13.     Else

  14.  
  15.         MsgBox "Mouse is not installed"

  16.  
  17.     End If

  18.  
  19. End Sub