Troubleshooting suggestions :
1. Run a full
virus scan to make sure the machine is clean. I use Malwarebytes (free edition). It is one of the best, if not the best, in the business.
2. Do a
disk defrag. Most will tell you to use the native Disk Defrag.
I don't. I use Auslogics.
Use whatever program you prefer.
Disk defrag is to improve performance by reuniting fragmented files so that the computer will run more efficiently.
3. Do a
disk cleanup. Again Windows has its own Disk Cleanup application.
I, on the other hand, use Ccleaner.
Disk cleanup is to help you free up disk space by removing obsolete files such as temporary internet files etc etc etc.
4. Run a
system file check to look for corrupt files. It will try to do repair if any found.
https://support.microsoft.com/en-us/kb/929833
If system file check says corrupt files found but unable to repair, use this method...........
Right click at Start button > click Command Prompt (Admin) > at the flashing prompt, copy and paste this command.........
dism /online /cleanup-image /restorehealth
press Enter key.
It will tak quite some time. When it finishes, it will give you a report.
*** In the reply above, I included some programs I myself use. It is by no means intended to make you use them. Just showing you my choice. That's all. ***