Maybe your OS/Windows/BIOS or whatever is setting the APM on back again ?
Check system configuration and try the drive with another system to confirm that the APM setting are sticking. Maybe you didsomething wrong ?
Try to power the drive off and on as soon as you set APM with hdat and make sure that the clicking on idle is gone. If so and if it only returns when you re-boot the system i would say that the OS is changing the settings again.
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