I was infected by U.Z.A.S O/S and my Antivirus Software could not detect it. It does nasty things like changing your wallpaper, disabling Taskmanager and Disabling Properties tabs. After analyzing the activity of the U.Z.A.S O/S on my computer I wrote a little utility to help you remove this virus/trojan or whatever it is. Get the utility from here.. It works on Windows XP. I don't time to write more.. Let me know of any issues. I worked for me somehow! Cheers!