Double-check your system for trojans, viruses and spyware.
Download TrojanHunter - trial avalaible, The Cleaner - trial available, a2free - freeware or ewido - freeware to check for trojans. (Update first before running a full system scan)
Run an online scan using Panda ActiveScan or Housecall.
Run a deep scan using Microsoft Windows Antispyware
Run a full system scan using your AVG (update it first)
Usual ZA Firewall, Spybot, AVG & more
Cable ISP with WI-FI
(Recent Email Received) "We have received reports that your account was used to send a huge amount of unsolicited commercial email during the recent week."
If this message is factual, how would I be able to tell it is happening? How would it manifest itself?