According to Microsoft's own site and I quote:
DISM: Deployment Image Servicing and Management (DISM.exe) is a command-line tool that can be used to service and prepare Windows images, including those used for Windows PE, Windows Recovery Environment (Windows RE) and Windows Setup. DISM can be used to service a Windows image (.wim) or a virtual hard disk (.vhd or .vhdx). DISM comes built into Windows and is available through the command line or from Windows PowerShell.
You probably read many articles telling you to use this to fix your system. But maybe your intimidated by the command prompt or the Powershell. Don't worry citizens, there's a free simple utility to help you.
It's called DISM-gui from: www.paehl.de/dism-gui
It downloads as a 7zip file. Decompress it and run either DISM_GUI_X86 (32 bit systems) or DISM_GUI_X64 (64 bit systems). I used this recently when I was having some video issues with my system freezing up so I decided to run this to be sure that no system files where corrupted.
In my case I clicked on the Repair button first and when that finished I clicked on the SFC button. So if you read an article telling you to run DISM or System File Checker, nothing can be easier.
By the way the commands for command prompt or Powershell:
DISM /Online /Cleanup-Image /CheckHealth
DISM /Online /Cleanup-Image /ScanHealth
DISM /Online /Cleanup-Image /RestoreHealth
