Hi, there seems to be some kind of trojan root kit in your computer .
Download malware bytes from malware bytes.com update it and run. It will show if any present in the computer in the Show result button after scan. Remove all the things by selecting individually.
Try to create restore points. If not solved, download Junk ware removal tools from thisusu by googling or download at bleeping computers.com. Run it . It runs in dos mode and fix most of the problematic programs,which could have been injected with your genuine downloads by some mischief sites.
If those does not solve , try sfc /scannow and if it runs 100%, check the system protected files integrity and then copy any files missing.
If not, better opt for repair windows
As the last resort, reinstall windows. There is no separate download available for this, as far as i know.