Sounds like you might have multiple problems, first of which would be your graphics card drivers. i would try reinstalling them.

How to Reinstall GFX Drivers

If you can't follow that, I would try googling 'reinstall drivers' or 'reinstall graphics drivers'

As far as viruses go, you should make sure you have a good AV software and make sure its updated!

Top Rated Anti-Virus Programs

Personally i wouldn't buy any, I would download a torrent of one for free.