ignys, I don't think you answered his question. I am also having his problem. MY computer is the one sending out the messages from those electronic places. They're sent to EVERY address in my Hotmail account and I am getting some nasty replies...and losing friends.
Scans show nothing, I have antivirus, adware/malware programs, and a firewall. However my Hotmail account sends out those messages about once every 2 months.
Any other ideas of what is wrong with my computer?