Having used a Happy Hacker Lite Keyboard for quite a few years, I'm used to having to use key combinations to page up, go 'home' or even to perform F4. Now that I'm using the Apple Wireless keyboard, through the lack of Apple providing standalone drivers, I need to make Vista work myself. On one hand I can understand why Apple don't want people using their peripherals on Microsoft machines which could be looked at as devaluing their brand. But on the other hand, not having drivers for Vista or XP mean that lots of people like me buy the shiney product without reading the small print and end up thinking 'argh! I hate you Apple!'. Other more sensible people do read the small print, buy a Logitech DiNovo Edge keyboard and always wish that they'd got the Apple one!
Coincidentally Logitech don't support the DiNovo Edge on OSX but the core buttons work out of the box and the extra buttons can be programmed using ControllerMate. That's a blog post for a different day!
Going back to the Apple Keyboard problem, the traditional way to re-programme a key press on XP or Vista is to use Randy's Sharpkeys to change registry settings to make the keys do other things. The problem with the Apple keyboard is that the 'fn' key simply doesn't register. This is where AutoHotKey comes in. It requires a bit more understanding that Sharpkeys but it works! Micha on the AutoHotKey forum wrote a HID DLL specifically for picking up the fn keypress. Thank you and hats off; I wouldn't know where to start!
How to get the fn key working..
Long version.. Read, understand and implement the guide at http://yotz.eu/fnkey/
Short version.. Download and install AutoHotKey. Go to the bottom of http://yotz.eu/fnkey/ and download the AppleWirelessKeyboard.zip file, put it somewhere sensible and add a shortcut to the Apple Wireless Keyboard.ahk file in your Windows Startup folder. Page up sorted!