SharePoint Designer 2010 is also free and available for public download. SharePoint designer 2010 available in both 32-bit and 64-bit. You can install SPD 2010 side by side along with SPD 2007. But, the limitation with this SPD 2010 is you cannot open the SharePoint 2007 sites in it. So, you have to use the specific SPD version for the specific SharePoint versions.