It certainly sounds like you've got some sort of malware on your computer. Try downloading Adaware from https://secure.lavasoft.com/products/ad-aware_se_personal.php - it's free and can sort out a lot of nasties. Another good one is Spybot S&D from http://www.spybot.info/en/index.html = If one can't find anything the other probably will. Also make sure that you carry out a full virus scan; you have got some anti-virus software, I hope.