The Visual Studio Extensions for Windows SharePoint Services (VSeWSS) is a set of tools for developing custom SharePoint applications. It adds project templates and project item templates to your Visual Studio 2008 environment and contains a SharePoint Solution Generator to generate Visual Studio projects from existing SharePoint environments.
By default the VSeWSS Extensions installation program only supports 32-bit machines, you cannot install VSeWSS on 64-bit machines. By modifying the MSI installer using Microsoft's Orca tool, available inside the Windows SDK, you can change the installer to add 64-bit installation support.
SharePoint Buzz already created a modified MSI for you. Download the VSeWSS 64-bit version of SharePoint Buzz.