Further details: Machine housing Yahoo Messenger is HP Pillivan A250n 2.8 GHz, 1.5 GB RAM, running Windows XP Home SP2. OS was restored by owner when system failed to boot. All previous software seems to operate. Owner uses machine mostly for chat and poker games from Internet. There is AV on system; but suspect there might be malicious software in machine. In addition, suspect that registry may be hosed up with multiple installs of Yahoo messenger. Can anyone suggest what might be one way of determining problem here and what can be done if any to restore the system.