Don't worry, time to time I receive an email from myself.

If you use Yahoo web mail, your computer has nothing to do with this. Someone had his computer infected and had your email in his address book, of course he used Outlook for email. Your email is added to a list together with the addresses of the address book and other's computer addres books. Then the virus begins to send email with spam or virus where the addesses of "from" and "to" are picked from the list. Some stupid virus don't check if "from" and "to" is the same address and so, you receive email from yourself.

Once your address was added to the list it begins to propagate to other infected computer and spreads everywhere. As the list has a limited length, within some time your address extinguishes being replaced by a fresh one from a newer victim.

Stupidity also evolves!