This is what inevitably happens to every computer running the Microsoft Windows
family of operating systems. Once your computer has been running for a while, the registry
and filesystem gets so full of useless junk from old programs and bloatware
, that it slows the whole system down. After you've defragged a million times and cleaned up everything imaginable, you still can't get your computer back to the way it was when you first installed Windows. The only cure is to reinstall a fresh copy of the operating system. That will keep you going for at least another 3 months.