VIA's official Microsoft Windows XP 4in1 drivers have just been uploaded to the Drivers Page. They are also updated for other operating systems. The installation utility has been updated. As always, if your system is stable there's no need to update your 4in1 drivers, however.
Basically they are drivers that enhance support for Via based board under the windows enviroment. Think about them as video card drivers for a Via motherboard, they add new compatibility, fix problems with the board and provide increased performance.