This is a short script useful to install GIMP and all its dependencies without further user intervention:

' This installs The GIMP and all dependencies (eg. GTK+)
Option Explicit

Const windowStyle = 8  ' Display as active app

Dim result, oShell

If result = VBNo Then
  oShell.run "gtk+-2.10.6-1-setup.exe /SP- /SILENT", windowStyle, True
  oShell.run "gimp-2.2.13-i586-setup-1.exe /SP- /SILENT", windowStyle, True
ElseIf (result = VBYes) Then
  oShell.run "gtk+-2.10.6-1-setup.exe /SP- /SILENT", windowStyle, True
  oShell.run "gimp-2.2.13-i586-setup-1.exe /SP- /SILENT", windowStyle, True
  oShell.run "gimp-help-2-0.11-setup.exe /SP- /SILENT", windowStyle, True
End If

' do nothing on Cancel
Set oShell = Nothing