I was able to successfully update my XP SP1 installation to SP2 on my MacBook. I used the offline installer, changing the uninstall directory from C:\windows\$NtUninstall$\ to a different folder in the root. I used C:\sp2\$NtUninstall$. I don't know if this will work for others, as this is the only machine I've tried it with. This was with boot camp 1.1.2, and after updating to 1.2, I have no unknown devices, and everything works great, trackpad scrolling, rmb, etc. Let us know if it works for you. 