Does Comcast also allow "Web Mail Access" to your email account via a web browser? Most ISPs, (Internet Service providers), do.
If so, open your browser and visit Comcast's web page, and log in to their email option with your email username (normally your email address), and password. That's the same password you use when opening Windows Live Mail.
There is a chance, (slim), that your WLM settings did not delete emails from the Comcast server when you downloaded them in WLM. If that is correct, then you may find a lot of your emails still available.
If that's successful then you have options.
If you haven't backed up your emails from WLM I think your only choice with that is to delete the account in WLM completely, close down WLM then re-open it and add this account again.
I somehow started to delete my comcast.net email account from Windows Live Mail, which is installed on my laptop. I caught it before it was complete but all of my folders disappeared except for 'unread' mail.....and when I next rebooted my computer, the all the email was gone - unread, sent, deleted, all the folders I use to organize mail. I cannot seem to restore it. There is no 'previous version' and I am not easily finding a backup through Norton. Any thoughts or help would be greatly appreciated. Neither comcast nor microsoft can tell me anything helpful thus far.