Imagine you have a Windows PC with a single user account, and you just lost your password. Here's how to enable the hidden Administrator account with nothing more than the install CD and some registry hacking magic so you can reset your password.
Normally if you wanted to enable the hidden administrator account from within Windows, you'd need access to an Administrator mode command prompt, but that won't work if you don't have access, right? This is a great way to quickly enable the hidden admin account so you can reset the password on your main account.