Sometimes if the problems you are having are to complex, it can be easier and quicker (thereby cheaper) to reinstall your operating system. 

Some companies would just reinstall and that's that, but I will do the following:
Back up all your personal files and saved passwords (if stored in the users directory),

 format the disk, install the operating system,

 download and install all the critical Microsoft updates (service pack 1 for Windows 7,  8.1 for Windows 8 and all updates for Windows 10) 

reinstall your main drivers , any free software you require and  set your system up.
 

I can also reinstall your printer, mp3 player, scanner etc.