The free SharePoint Designer 2010 RTM downloads for both CPU architectures are available on Microsoft’s download site:
As we have noted in a previous post, SharePoint Designer 2010 will only work with the current SharePoint 2010 versions (previous blog post).
We need to have SharePoint Designer 2007 installed in order to work with Windows SharePoint Services v3 or Microsoft Office SharePoint Server 2007.
Microsoft Small Business Specialists
Co-Author: SBS 2008 Blueprint Book