To find inside an email in Outlook:

* Double-click the message to open it in its own window.
o You cannot search inside a message shown in the Outlook preview pane.
* Press F4.
o Alternatively, click Find in the message’s toolbar in Outlook 2007.
o In Outlook 2002 and Outlook 2003, you can also select Edit | Find… from the menu.
* Select your search options.
* Use Find Next to find all occurrences of your search terms

While there is also a Edit | Find Next menu item in Outlook 2002 and Outlook 2003, you have to keep the Search dialog open. There seems to be no way to make use of the Find Next command.