You might want to try to run the Virus Scan and the other applications in "Safe Mode with Networking" which is reached by tapping F8 repeatedlywhile booting up - giving yo safe mode with Internet access as per this document http://community.mcafee.com/docs/DOC-1294
If that does not help and while you are still in safemode go to http://www.malwarebytes.org/mbam.php and download, install update and reboot when asked. It works in this mode.
Just wonder if you are positive these emails are actually coming from your computer becasue they can also happen if someone else has a problem and they have your email address in their address book.
It could be that someone you know who has your email in their address book is infected as there are certain bugs that mimic people when they generate emails. Was anything actually showing in your sent mail or out box?
Aside from the scans in 'Safe Mode with Networking" suggested by Tom/k3tg which is an excellent idea, you might want to post a Hijackthis log on one of the following forums for expert advice:
Do not post Hijackthis logs here, we can't help you with those !
Post the logs at one of these specialist Forums:
Be sure to read all the sticky announcements/instructions at the top of each malware forum!