Hi! I have solution for this problem. I read abuot that maybe 1month ago. Simply and accurate.

Boot your Leopard with -s (single mode)

when system start properly and coursor flashing type:

type:
/sbin/fsck -fy (hit enter)
/sbin/mount -uw / (hit enter, type exactly the same with "/" at the end)

type:
passwd root (hit enter)
type your new password (hit enter)
retype your new password (hit enter)


Leopard had know about that change so type:

touch /var/db/.AppleSetupDone (hit eneter, don't forget "." before Apple)


type:
reboot

Well done, now you are able to login to leopard on root account. Of course you can add some account after login.

Best Regards.