ThinkPad T430s and T430si models, with Optimus graphics, cannot be set to Integrated (Intel) or Discrete (NVIDIA) video only and install a supported Lenovo provided video driver.
There is no Discrete graphic only option within the BIOS configuration utility of the T430s and T430si. Setting the system to Integrated only will allow for VGA video only. There is not a supported Intel video driver for Microsoft Windows XP on Optimus models. Only ThinkPad T430s and T430si with Integrated video only are supported with Microsoft Windows XP.