Open System Mechanic and look to see if it has a restore button or some means of reversing the previous operation(s). Registry cleaners are a bad idea as they are pretty-well guaranteed to delete something important and cause headaches down the line. Windows has its own cleanup tools and they are all you need.
The other thing to try is a System File Check see this tutorial: System Files - SFC Command
There is also a chance of infection here of course so download the FREE version of Malwarebytes, update and run a full scan. Malwarebytes : Malwarebytes Anti-Malware PRO removes malware including viruses, spyware, worms and trojans, plus it protects your computer
- make sure it's the free version and not the trial of the Pro.
If it wont install in regular mode, try "Safe Mode with Networking" reached by tapping F8 repeatedly while booting up. It will also update & scan in that mode.