Windows 10: https://www.microsoft.com/en-us/download/details.aspx?id=45520
Windows 8.1: http://www.microsoft.com/en-us/download/details.aspx?id=39296
Windows 8: http://www.microsoft.com/en-us/download/details.aspx?id=28972
Windows 7: http://www.microsoft.com/en-us/download/details.aspx?id=7887
Windows Vista: http://www.microsoft.com/en-us/download/details.aspx?id=21090