|If you can't get online it probably means that use proxy is intiated in your browser:|
Open IE and click on tool/internet options/connections/Lan settings and uncheck use proxy server.
See if you can get back online, then download Malwarebytes
fix all it finds
You have no reason to re-install your OS as suggested in Response #1
That should always be a last resort as the person answering your question has NO idea of how many progs, etc are installed on your PC.
It is however a GREAT idea to back up all your important documents and files on a steady basis in the case that you might have to do that one day.
Some HELP in posting on Computing.net plus free progs and instructions Cheers