First, disable Fast Boot if enabled. While it has the word 'Fast' in it's title, it's anything but in a lot of cases.
Secondly, try updating your graphical drivers.
Third, you can do a clean install of the OS.
If after the clean install it's still slow, it's hardware based. If that's the case, that's up to you to improve the parts you have.
Another bit that might be a good idea, is to back up your system regularly with a snapshot tool (i.e. RollBack Rx or Comodo Time Machine) especially if the system is much faster at the installation of Windows then it is later on.