This type of behaviour can be caused by malware. Try running several malware scanners. It is best to run several as each will pick up things that the others miss. Some scanners you can try are: * [http://www.malwarebytes.org/mbam.php Malwarebytes] * [http://www.superantispyware.com/ SUPERAntiSpyware] * [http://www.lavasoft.com/products/ad_aware_free.php Ad-Aware] * [http://www.microsoft.com/windows/products/winfamily/defender/default.mspx Windows Defender] * [http://www.safer-networking.org/en/home/index.html Spybot S&D] If the above malware scanners don't find it or can't clear it, post in one of these forums for specialized malware removal help: * http://forums.spybot.info/ * http://www.spywarewarrior.com/index.php * http://forum.aumha.org/ * http://www.bleepingcomputer.com/forums/ * http://www.spywareinfoforum.com/