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 do not find any malware or can not clear it, you should consider posting 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/