[dnanian]

You can't restore to a drive you're running from. But that's not a problem... usually.

This might be difficult, because you're trying to copy from an Intel Mac to a Power PC Mac. But, you can try starting up from the backup by holding Option down during startup, and selecting the drive. Once you're running from the backup, you should be able to restore to the internal.

If you can't start up from the backup (because it's set up for your MacBook Pro), you'll want to clean install Leopard to your PowerBook. It'll prompt you to 'copy from another Mac': point at the backup volume and it'll bring in your applications, accounts and data.