Hello Jignesh. This issue has been reported before by other users, and it turns out it's the effect of malware. In other words, your system is infected. To scan for malware, install, update and run these programs ''in this order''. They are all free for personal use, but some have limited functionality in their "free mode", but the features you'll miss are not really needed to find and remove the problem you have. Remember that ''not all programs detect the same malware''! Malwarebytes' Anti-Malware - [http://www.malwarebytes.org/mbam.php malwarebytes.org/mbam.php] SuperAntispyware - [http://www.superantispyware.com/ superantispyware.com] AdAware - [http://www.lavasoftusa.com/software/adaware/ lavasoftusa.com/software/adaware] Spybot Search & Destroy - [http://www.safer-networking.org/en/index.html safer-networking.org/en/index.html] Windows Defender - [http://www.microsoft.com/windows/products/winfamily/defender/default.mspx microsoft.com/windows/products/winfamily/defender/default.mspx] Dr. Web Cureit - [http://www.freedrweb.com/cureit/ freedrweb.com/cureit] If these don't find it or can't clear it, please tell me and I'll provide you with further assistance.