my pc is sending spam, but webroot scan shows nothing. what to do?

Hello 23mupton,

Welcome to the Community,

Please have a look here http://www.microsoft.com/security/online-privacy/spam-prevent.aspx

Also it's possible you could also have some PUAs https://community.webroot.com/t5/Techie-KB/How-to-Remove-Potentially-Unwanted-Applications/ta-p/40744

Let us know if you have more questions,

I hope this helps!

Just to add, that a password change on your email account would be a first step also, as your account may have been compromised.
How have you established that spam is coming from your account?
 
Best to notify your ISP, and you might also like to Submit a Support Ticket  for peace of mind, and certainty.
 
Please see: What to Do if Your Email Account Gets Hijacked and Sends Out Spam | The Mac Security Blog
 
    Outlook sending emails to all my contacts containing spam from me - Microsoft Community
 
   Rogue Emails in Sent Items - BTCare Community Forums
 
HTH.