Outlook 2003 Default Format Style

I need to know how to set the Outlook 2003 default Format / Style. Using Outlook 2003 in essentially default configuration. When creating a new message, it appears to double space. On investigation under Format / Style, Paragraph is selected which causes this. If Normal style is selected all is good, except only for the current message. A new message will default back to Paragraph style. How can I default this to Normal style (like everyone elses’!).