I have a S4XP with Windows Vista Business installed. To get the MS slot working under Vista use the Windows XP driver, get it from the Sony website.
To get all your FN keys do the following:
(taken from the sony website)
Install BIOS update*
Install Sony Utils.dll
Install Sony Shared Library
Install Sony Video Shared Library, Setting Utility Series*, VAIO Event Service, VAIO Control Center, VAIO Action Setup*, VAIO Power Management*, Battery Checker*, AV Mode Button*, Appmon*, Instant Mode*, VAIO Camera Utility*, Wireless Switch Setting*
Install remaining donwloads*
* Only if applicable.
** Most XP drivers will work in Vista. We provide Vista download drivers only if XP drivers do not work and there are no supported Vista inbox drivers. This means that, for some built-in devices such as the Memory Stick, Motion Eye camera, etc., you might have to install the appropriate XP drivers in case you perform a clean installation of the Vista OS. XP drivers can be found on the VAIO recovery disc or on our website (see preinstalled drivers).
You can get all you need from the sony website.
Up to this point everything worked fine for me, except brightness control. The S4XP has a Geforce Go 6200 display adapter. Replace the driver that came with Vista or through Windows Update with driver version 98.12. Download this driver directly from NVIDIA. After a reboot all the FN keys are working.