run these commands in terminal:
sudo su (enter your password after this line)
mkextunpack -d /DVD_Extensions /Volumes/Jas\ OS\ 10.4.7/System/Library/Extensions.mkext
(Your DVD name may be different so replace the "Jas\ OS\ 10.4.7" part with whatever yours is called, noting that the \ after a word is needed in order to put a space in. This will extract all of the extensions in the mkext file into /DVD_Extensions.)
All of the extensions in this folder are flattened meaning that anything that would be in a plugins folder within a kext is now located right next to the kext that would normally contain it. This means that the AppleGenericPCATA.kext that is normally in IOATAFamily.kext/Contents/Plugins/ is now located in the /DVD_Extensions along with IOATAFamily.kext. This means that if you're adding a new kext that contains plugins, you will need to place each kext into the /DVD_Extensions folder. This shouldn't matter if you're using kexts without plugins.
After you add the kexts you want in the bootup Extension.mkext, run these commands:
chown -R root:wheel /DVD_Extensions
chmod -R 755 /DVD_Extensions
now you'll be able to run the kextcache.
kextcache -m /Extensions.mkext /DVD_Extensions
this will now create a new Extensions.mkext on your root / folder which you can then use transmac or whatever to replace the old one.
If you're in Mac, you can mount the image as readwrite by doing this:
hdiutil attach /"Your Image Name Here" -readwrite
This will let you copy the files directly to the image.