Until recently once I downloaded my mail into Windows Live mail it dissappeared from my Yahoo Inbox. Now it stays there until I go back to BT Yahoo Inbox and delete it. I can't find an ooption to change this.
In your Windows Live Mail go to the Tools menu - then select Accounts. Highlight your mail account and click Properties. On the Advanced tab untick the box beside Leave a copy of messages on server - click Apply and OK.