Hds which are relatively new park automatically when you shut down the computer.
There is no need to "undo" the parking, because any disk access does this automatically.
If your hd needs parking, don't rely on reading an empty directory. This will temporary position the head somewere in the middle of the hd. First, if that dir is present in the disk cache, there will be no effect. Secondly, any hd access (by the disk cache for example), will move the head. Third, even if the head remains there, when you move the computer you may damage that area of the hd. The hardware "landing zone" is in a safe place outside the usable area of the hd.
I have a very old AT with a 20Meg hd, and for this one parking is done using the CMOS Setup. I think I once had a separate parking utility, but don't know were is it. If I find it (little chance), I will send it to you.