Stealth Email Take-over?

WinMe: I received a (Hotmail) "mail delivery failure" notification from 4 email addresses I know nothing about. So, is it possible someone has gotten control of my system or has scarfed my email address from a website I have (listing my property 4 sale)?? To enable Hotmail to send these fakes, wouldn't they need to sign in with my password? Any help / suggestions would be appreciated.
(I'm using Sygate & AntiVir Guard.)
P.S. Thanks to those who helped with my last

 

This is actually a common occurrence called spoofing. The way in which it usually comes about is someone who has your email address in their address book (most commonly outlook express) has a virus on their computer. The virus is harvesting address from their address book and sending itself to whomever using your email address as the sender. When these spoofed messages are undeliverable, you receive the mail delivery failure notice just like if you had in fact sent the message yourself.

Do you send recieve your hotmail via the web or do you download it it using Outlook Express, ThunderBird, etc?

If you are at all concerned you may have any infection on your computer I urge you to follow the steps provided in our READ & RUN ME FIRST Before Asking for Support and attach the logs from BitDefender, ActiveScan and HijackThis for review.

 

I access my Hotmail thru Firefox.
Thank you, Abby Sue, for your explanation.