nobody needs macjanitor.
1) open netinfo manager, authenticate yourself as admin user, enable root account
2) open terminal, type "passwd root" and select your root user password
3) type "sudo /etc/daily"
4) type "sudo /etc/weekly"
5) type "sudo /etc/monthly"
these last three commands are the ones that macjanitor tries to run. and these commands are run automatically if your computer is always on. this is standard unix maintenance by the way, and if you are not familiar with unix, i must warn you to keep the root password really safe because root is THE superuser that has access to everything in your computer.
maybe macjanitor fails to run the scripts because it lacks permissions? but don't worry, after you have set your root passwork (first two steps) you can be a macjanitor yourself and actually know what you are doing there

after the first time, you will only need to repeat the last three steps because the root is already enabled.