Shouldn't Excel 11 be located in HKLM\SOFTWARE\Wow6432Node\Microsoft\Office\11.0\Excel\InstallRoot\Path on a Winx64 machine? Also, if the user has Excel 2010, then wouldn't the only sub-key underneath Microsoft\Office\11.0 be "common"? On my machine running Winx64 and Excel 2010 x64, HKLM\SOFTWARE\M...