yahoo mail sent suspicous web addresses to all contact

Malware detected in email databases has to be cleaned up by you. You have a few choices:

1. delete the whole file which is not an option you normally want to use
2. load the email folder that contains the infection and delete ALL unnecessary emails (hoping to remove the problem email) and then use the Mailbox Cleanup option to delete all old emails. Then compact the Outlook database to permanently remove data. See http://support.microsoft.com/kb/196990 If you do not cleanup and compact the databases, the deleted emails may still be leaving hidden information in the database that you just cannot see but a scanner may still pickup on it.
3. create a new folder and move only emails you really need into the new folder and then delete the infected folder.

What email program are you using? IF hot mail, read this:
http://blogs.msdn.com/b/securitytipstalk/archive/2010/07/07/hotmail-hacked-take-these-steps.aspx

 

Hope you can get it straightened out.