My hotmail is sending emails everyone in my address book every time I email – how can I fix this?

I received an email from one of my friends and later found out she hadn't meant to send it. Since then, every time I send an email it sends the one I received from my friend to everyone in my address book - I'm guessing this is what happened to my friend.  I deleted the email as soon as I realised this had happened but still my hotmail keeps sending it to all my contacts every time I email something else.

I thought at first that it was a bug in my laptop so have run every debug programme I have but accessed my hotmail account from my work computer today and the very same thing happened again.

Can anyone suggest how I can fix this please??