For Laptops, the hard disks, in my opinion, installed are modified in such a way that it is designed to withstand weak bumps and basic moving. From everyday mobility to moving it from your house to your car, when you're handling it, then to your office. It's modified to withstand those and the makers of your laptop is expecting those scenarios.
As you can see in the image above, that is a opened hard disk. The disks in the middle is spinning when used and the arm that is reaching in the middle is the reader/scanner. That is the one that reads/writes in your disks. That is a multi layered hard disks. All modern hard disks are built this way that they are over one another. The distance between the disk and the reader is 0.002-inch (51-micron). Now you know what i'm talking about earlier. Physics states that when the hard disks spins, theres' something that happens around the disks that makes the distance between the disk and arm. And when the computer is shutting down, the arm will first stand aside then the hard disks will slow down. Look at my references for more details.
Is the hard disk spinning when the computer is sleeping?
From what I read, the hard disk is still spinning but at a slower rate. Because at the description is says, it uses much less power to the computer. How can you stop the hard disks from spinning?
1.) Go to control panel under the start menu. For Windows 8 and 8.1, right click windows in bottom-left and choose control panel.
2.) Click on "Power Options".
3.) Click on "Change plan settings" on the active power plan.
4.) Click on "Change advanced power settings".
5.) Scroll until you find "Hard disk" then click on the plus button and another plus button.
6.) Change to the desired values.
Will forcing the computer to shutdown damage the Hard Disk?
No, it will not damage the hard disk however; The data stored in the disk may be lost or get corrupted. This is different from unplugging the computer from the AC. But, you will hear a noise inside the computer which makes you worry more. Don't be troubled by this noise, it's just the arm returning to it's resting position and clapping to the base of the arm. Because of the safety feature that when power is lost, the arm will automatically return to it's resting position.(See reference below)
Does the remaining free space affect the Hard Drive?
Yes, it does affect the hard drive. First is your space is depleted(obviously). And reading speed is affected because the reader must read all the files that is stored in the disk rather than skip the "not filled spaces" ones.
What is Hard Disk Defragment/Defragmentation?
This is a trick in the hard disk. When you are storing files in the disk, the arm just puts it on where on the part on the disk is free space. Later on, when you try to access those files, the data is scattered all over the hard disk. Defragmentation makes these files that are stored everywhere be together by moving the data that is the continuation of the previous data next to that data. Making the read/write faster and not that complicated and scattered for the arm to search.
So, what's the difference of HDD(Hard Disk Drive) and SSD(Solid-State Drive)?
Image: SSD(Left), HDD(Right)
Let's just say that SSD's are much faster than HDD's because there's no moving parts.(Wow that's very simple)