Perform the following operation.
->If your pc is slow then perform Disk Clean up on all hard drives.
->Then run Disk Defragment utility.
Addition to Harkdik's opinion -
-> Use
CCleaner and then clean up unnecessary files and startup items that start up when you boot up your computer.
->
Advanced SystemCare is another good software which performs some additional tasks such as spyware removal, shortcut fixer, etc.
(Recommended)
->
Glary Utilities is another good software.
I recommend going for CCleaner along with Advanced SystemCare or Glary Utilities.