i've had this issue with my last video card. try reinstalling your nvidia drivers and do a custom install. make sure you check the box next to "clean install." the tearing shouldn't occur with the 320.14 driver and be sure to NOT force vsync.
as for your harddrive issue, i'd download the free version of malwarebytes, make sure it's completely updated and run a quick scan of your hdd that is running slow. i also recommend using the free version of avast anti-virus software for now on especially when visiting those sites you mentioned.
have a great weekend, let me know if you need anymore help, and we'll see ya in the endzone!