It sounds like you may have been infected by a Trojan worm. To keep your computer safe, you need to have good firewall, anti virus and anti spyware programmes installed in your computer and, most importantly, keep them fully and regularly updated. Here are links to some free such programmes and good luck: - http://www.zonelabs.com/store/content/company/products/trial_zaFamily/homeofficetrial_zaFamily.jsp?dc=12bms&ctry=GB&lang=en - http://free.grisoft.com/doc/2/lng/us/tpl/v5 - http://www.majorgeeks.com/download506.html - http://downloads-zdnet.com.com/3000-2144-10122137.html - http://www.majorgeeks.com/download3045.html - http://www.microsoft.com/athome/security/spyware/software/default.mspx