OWA 2010 provides the same conversation view and experience as Outlook 2010: By default, messages are displayed in threads so that all the messages on a particular topic are grouped. No more searching for a previous message to check what the response is referring to. When a new message in a thread comes in, the whole thread gets moved chronologically to the date/time of the new message. Conversation view has its benefits and drawbacks, but if you don't like it, you can turn it off. Just right-click Arrange By, scroll down to Conversations, and deselect Show Messages in Conversations.
1. Right-Click Arrange by: Date.
2. Uncheck the Conversation box.