http://office.microsoft.com/en-us/buy/using-the-product-key-card-FX101853163.aspx
Alternate link if that one doesn’t work:
https://www20.downloadoffice2010.microsoft.com/usa/registerkey.aspx?ref=pkc
If you need to reinstall your Microsoft Office 2010 software, you can download or order a backup DVD. You will be required to provide a valid Office 2010 Product Key.
http://office.microsoft.com/en-us/products/microsoft-office-2010-backup-FX101853122.aspx?CTT=5&origin=HA101847520
Alternate link if that one doesn’t work:
https://www20.downloadoffice2010.microsoft.com/usa/registerkey.aspx?ref=backup)