It sounds like your account has been comprimised. Chnage your password ASAP, run a virus checker that will check the registry and hard drive / mail accounts. That should certainly help.

is it a hotmail account by chance ? ,i’ve seen a few recently where a infected e-mail is on the hotmail server and sends multi e-mails from there .only way is to take a note of all your contacts numbers etc either in a text file or good old pen and paper ,delete everything from hotmail ,folders ,old mail contacts everything and change your log in details .

Then enter your contacts details again by hand create new folders and your back in buisness.

if its a virus in your Pc ,then switch off system restore ,run a virus check .then if it kills any virus’s then turn system restore back on ,might have too run a antivirus in safe mode