Are you talking about #29? Repair Windows 8 Component Store?
That windows command is notorious for taking a painfully long time, yet at other times it only takes 10 min. It gives no progress indicator at all either. But it is a risk to stop it in the middle of it because it is working with the windows files. That repair just runs the two commands
Dism /Online /Cleanup-Image /StartComponentCleanup
Dism /Online /Cleanup-Image /RestoreHealth
Running the repairs in safe mode is always the best idea to do, because if any 3rd party program gets in the way you can have problems happen. Are you able to boot into safe mode?
Shane