Problem after doing Microsoft version of reset/clean install

[Bill Pert]

A couple of days ago I decided to use the Reset option (Remove Everything) as per instructions in the Updates section of Windows 10. I only did this because my machine was getting slower and slower even though it was very stable. Since the reset my machine, even though I have not put anything apart for required files EG. Anti virus etc onto the machine it is behaving quite erratically, the mouse locks up, pages taking for ever to load etc etc which is quite annoying as I cannot pin it to any one source apart from Windows 10. I have upgrades all the required drivers and video but this has not helped one bit. Apart from throwing this machine against the wall and calling MS every word I have learn't over the years, can someone please tell me how to get around this problem. I was thinking of putting another copy of windows onto the HD but don't know if it would accept my Serial No as it would not be a legal copy. I did notice that even though I selected Remove Everything, I still have Directories on the HD that I thought should have been removed, so much for a Reset/Remove Everything.
Windows10 x64, 16g mem
Thanks
Ropar