In that case you might need to uninstall, then use a product like CCleaner or Revo Uninstaller to erase the left-over registry entries, then reinstall. You may also need to manuall delete any of the Office initialization files & folders that an uninstall leaves behind before reinstalling (backup your data first!!) - see 'Method 4: Remove Microsoft Office 2010 suites manually' at
http://support.microsoft.com/kb/290301 for details.