Hotmail displays a reading pane for displaying the content of the email message in your Inbox.
But if you want to turn off the reading pane so that you can see more number of messages in your Inbox then you can do this by using Options menu. Click on the Options menu available on the right hand side (above your Inbox).
Select Off from the available menu list. This would only display the list of messages in your Inbox with out any reading pane.