Finding lost Outlook emails

A customer recently had a hard drive die I had data recovered by a data recovery company. Luckily most files were recovered. A new hard drive has been installed. He uses Outlook 2007 and had not done a backup of any outlook folders/messages. I need to somehow find his emails and import them back into Outlook. Where do I find the emails within the Outlook program folder? How do I get them back into outlook?