windows 7 home premium upgrade key

I just bought a used 2007 laptop that has Buy Windows 7 Ultimate Product Key but no Microsoft Office 2007 Professional. Can I download Microsoft Office 2010 Professional Plus Serial Key onto my old laptop or do I need to get the 2007 version. I want 2010 so I can have the new “note” software for college. If I can download will it slow down my laptop?