File extension redirect?

sounds like you have a browser hijacker. Start by cleaning your PC of those viruses. You can download MALWARE BYTES free as well as AVAST personal edition from a reputed site like softpedia.com (also free) run both programs in FULL scan mode and you should be rite as rian. You can download another free tool ccleaner, just put www.ccleaner.com in your browser & download & run , this will clear all the temporary files.