Lost Outlook 2003 contacts

Hello,
I have a real dilemma!
I have just upgraded to Microsoft Office Pro 2007 from office 2003. I had made personal files in my e-mail box(2003) and I may have done it wrongl because now, I can only access 5 of my contacts. I did have files in my old Microsoft office Outlook... How can I retrieve these other contacts that have dissapeared after upgrading? I know that they must be somewhere on my PC????
Thanks for your help
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