Please try to install the Antivirus sotware , you can install any of the free antivirus software. Example Avg
and scann the computer for virus or trojan horse , spyware .
look of all the things i can tell you now since i cant get in your registry or on your harddrive from here go to google and get "spybot search and destroy" that should be a big help and will take care of nearly any problem you could be having.