to make sure your mach_kernel doesnt get overwritten look on the root of your hardrive. then go to Extra, then right click on com.apple.boot.plist and click get info, click the lock at the bottom and change it so everybody can read and write. then when u can write to the file, open it and go to where it says Mach_kernel in the quotes and change it to mach_kernel.voodoo if thts the kernel your using. then just install the update. after you may need to patch your sound again, video drivers, and System.kext(to fix mounting issues, system.kext will have to be updated to 9.5.5 AFTER you install the update, search insanely mac forums. i suggest backing up all your kexts so you dont have any trouble if the need to get some back arrises.

good luck!
edit
also, just go to the root of your hardrive to make a copy of the mach_kernel and just copy it to the desktop, or someplace easy for you to remember.

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