Hi there, You are using the wrong terminology .. you just want to spin down the disk and put it to sleep not park it, these days hard disks park themselves automagically (not like ye'olde days you know ;-)
I remember seeing a application on Aminet that would do it ... ah here it is ...
http://www.aminet.net/disk/misc/HDSleep.lha bit old but might do the job, there are certainly more apps around that'll do the same.
Regards!
