Can you get online at all? If you can, download malwarebytes and run a scan with that - it's very good for clearing out this sort of infection. Read the guide on using it for more info:
- this guide also has a link to download it
Remember to update it before you run the scan. If you can't get it to run, try running it in safe mode (tap f8 when you're booting up your computer and choose to start in safe mode with networking)
Just to be on the safe side, download/update and scan with superantispyware too.
If that doesn't seem to sort things out, post again and more expert help will be along - if you do need more help, they may ask to see your malwarebytes & superantispyware logs so be sure to save them.