Run something like HD Valet ( get rid of all the crap and temp files)reboot twice,then turn off all running programs including anti virus (actually it could pay to uninstall the dam thing but you will have to manually clean the registry ) then de frag. then reinstall op systen over the top.then defrag again
I am brutal with cleaning the HD and registry but with each step I reboot 2x
when everything is running smooth re install the antivirus
After HD DriveValet you can run a test before the real thing. Dump everthing there is nothing you need to uncheck