Office 2007 Media

I have a dell inspiron 1720, service tag <ADMIN NOTE: Service tag removed per privacy policy> which I am in the process of rebuilding. It came with office 2007 pre-installed. How can I get hold of the media to reinstall office 2007? I have tried the Microsoft site to download media but this only seems to be for retail versions of office, as when I put my product key in, it states it is invalid. Microsoft states that they do not get involved with OEM versions of the software and that I should get in touch with Dell directly. However, Dell refers me back to Microsoft. How do I get this resolved please?