Once I upgraded Office 2003 to Office Home and Student 2010. Then, I decided to install Office Home and Business 2010. When I tried to uninstall Home and Student 2010, I got an error message saying an office 2003 installation on your computer is corrupted and set up cannot continue, remove or repair the Office 2003 products and re-run setup. I reinstalled the 2003 and uninstalled it, then I could uninstall the Home and Studnet 2010. Although there was no Office installed, when I tried to install the Home and Business 2010, I got the same error message about Office 2003 installation corruption. Then I installed the 2003 and uninstalled it as it worked for uninstalling Home and Student. However, I tried to install Home and Business, I got the exact same message as above. I don't know if upgrading from 2003 to 2010 changed the registry and it still affected it.