There are a lot of driver missing when downgrade from xp to vista and 7 unknown devices is quite a popular topic discussed. And there are also other driver such as co processor. When downgrading for me the essential driver is chipset, sound, vga, wireless, bluetooth and card reader. So what to do with missing driver, for me if nothing wrong with your laptop no need for you to update the driver because you already have the essentials drivers.
Extract the files and right click on machine.inf select install.