You can't. What all do you have in Outlook 2007 that you want to move back to Outlook 2000? If Contacts, for example, you might be able to export to a .CSV file and then import that to Outlook 2000. But, if you try this, be sure to backup your Outlook 2000 first.
How long in that Office 2007 trial period? Only a month, isn't it?