Download the voodoo kernel installer from here http://code.google.com/p/xnu-dev/ Even though you are running voodoo now still run the installer and reboot. This will add the mach_kernel.voodoo flag to your com.apple.boot.plist for you so you won't have to mess around editing it and ensure that voodoo doesn't get overwritten by the update. Now before you download the update open your hard drive and go to System/Library/Extensions and copy your System.kext, seatbelt.kext, and any kexts you need for graphics or sound to a new folder on your desktop. Note: if you don't have kext helper get it from http://www.cheetha.net/Kext_Helper/Software.html it will make reinstalling your backed up kext files easier. Next get the update and install it, reboot and pray, your machine may auto reboot once during the first boot of 10.5.7 this is normal. If you can't get to the desktop or have a corrupted screen boot with -x to get into safe mode. Once to a desktop run kext helper and drag your backed up kexts into it, type your password and click easy install. Reboot and pray once more. If all went well you should have 10.5.7 now installed and running. I can't guarantee that this will work for you, but it's worth a try.