Dell inspiron hard disk

Getting a hard drive to idle down or stay asleep after a set duration of time is a next to impossible task with modern versions of Windows, because background services and processes are constantly accessing the drive. It's more doable if the hard drive is just being used as secondary storage (for personal files) with no programs installed or running from it. If that's the case, there maybe a program accessing that drive every now and then, causing it to wake it up from sleep and spin back up. You'll will have to find out for yourself which program or process is the culprit. Otherwise, you can replace the hard drive with a SSD for silent operation and less wear.