Sounds like Malware. Install, update, and run these programs in this order. They are all free for personal use, but some have limited functionality in the "free mode" - but those are features you really don't need to find and remove the problem that you have. '''(Not all programs detect the same Malware.)''' Malwarebytes' Anti-Malware - [http://www.malwarebytes.org/mbam.php] SuperAntispyware - [http://www.superantispyware.com/] AdAware - [http://www.lavasoftusa.com/software/adaware/] Spybot Search & Destroy - [http://www.safer-networking.org/en/index.html] If these don't find it or can't clear it, post in one of these forums for specialized malware removal help: [http://www.spywarewarrior.com/index.php] [http://forum.aumha.org/] [http://www.spywareinfoforum.com/] [http://bleepingcomputer.com]