Try booting in safe mode.
While in safe mode try the following:
1. In command prompt while running it in administrator mode type: "chkdsk".....without quotes.....if it finds errors for now do not accept its prompt to repair windows on next boot. This is just too check if windows installation is corrupted but if there are viruses lurking there is no use repairing windows at this time.
2. Run a scan with malwarebytes anti malware and quarantine any infections.
3. Download adwcleaner and roguekiller, run either one, if it finds any issues let it clean the computer then reboot again in safe mode and run the second one.
4. Now boot into safe mode again and now run "chkdsk" again and see if any issues are found, if there are issues, accept its prompt to repair when rebooting the computer as normal.