Restart the computer and while it's starting up, hold command-S. This will start up in Single-User Mode, which gives you a root command line. At this point, type the following commands:
Code:
mount -uw /
cd /private/var/db
rm .AppleSetupDone
exit
Your computer should now allow you to create a new administrator just the same as the first time you turned it on. From here, you can do whatever fixes you need.