|"reboot" just means to restart - you mean restore.|
For that we need the make and model number of your computer.
If there is a hard disk error this could stop defrag from running.
Type chkdsk /f in the Run box and hit Enter key. This will do
a scan on startup. There is also chkdsk /r which is more thorough so will
take a lot longer.
Have you checked for viruses? Try MalwareBytes on it, from here:
Run your AV scans too.
Make sure you haven't got too many unwanted background programs running.
There is a free program called CCleaner that can get rid of a lot of unwanted junk:
Always pop back and let us know the outcome - thanks