The Superfetch Process describes itself as one which "maintains and improves the system over time". What this means is that pre-loads programs which it thinks you'll use in an attempt to save memory. However, this usually takes more memory than it saves, and it doesn't always guess right.
Ironically, the best way to save your system is to allow it to calm down by not over-exerting itself with the Superfetch process.
Cancelling the 99% Hard Disk Process In Windows 8
Go to start and search for "Run". When you're here, type " services.msc " (without the quotes) into the box and press OK.
Go To Superfetch Properties
Scroll down the "Services(local)" list to "Superfetch" and right click, before clicking on Properties.
Set Start-Up Type To Disabled
It should open to the "General" tab, click to it if it doesn't. Click on the drop-down box next to "startup type" and select "disabled". Then click "Ok".