All stock xbox hard drives are locked to the xbox motherboard. There's no need to unlock them. Yes, your regular stock xbox is fine. You don't need another one unless you plan on putting games on the hdd.
Should you wish to unlock your hard drive, simply use FlashBIOS 3.03, EvoX Dashboard, UnleashX (settings menu), or ConfigMAGIC v1.6 Final to lock/unlock the hard drive.
You really should look at the FAQ section
on this site. You've asked some rather basic questions that all would have been answered if you simply took a few minutes to read.
Here's a good start: Things you should know about the xbox