Virus

I was wondering anybody could help-I keep getting strange Spanish e-mails to my hotmail account with an "unsafe attachment", presumebly a virus?
Sometimes they come from friends of friends so it might be bouncing through adress books?
Can anybody shead any light?

e-mails have been sent from my account to various companies, who have sent e-mails back to me in turn telling me to stop sending emails with virus's. Don't know how this virus works but its annoying.

Anyone know?