How do i change the boot animation on AOSP CM7

Boot animations can be flashed from the SD card in recovery.
Works on reborn rom
 
Did you name it properly? I looked at the thread you linked and it is refering to boot animation sounds. For a boot animation (video not sound) make sure you name it -bootanimation.zip. Then place it in the folder I mentioned in my earlier post. I've used the file manager method in every rom I've installed. That includes Reborn, Aphrodite, Harmonia, Rodimus, Bumblebee, and aosp.