If you are using Outlook Express to access Hotmail, please note

In June 2009, Microsoft announced a change to the way Outlook, Outlook Express, and Entourage programs access Hotmail which may require customers to take action.

To continue to receive e-mail from your Hotmail account, please select one of the alternative solutions below before September 1, 2009. After this day, new e-mail can only be delivered to your mail programs through the following alternative solutions. However you can continue to view your e-mail via the web....

http://windowslivehelp.com/solutions/dav/archive/2009/05/04/accessing-hotmail-on-outlook-outlook-express-or-entourage.aspx