Microsoft released the production versions of Windows Mobile Device Center (WMDC) for Windows Vista on January 31. WMDC replaces ActiveSync for Vista users. There are two versions available…
Microsoft Windows Mobile Device Center Driver for Windows Vista (x86)
Microsoft Windows Mobile Device Center Driver for Windows Vista (AMD64)
Please note that you must check which version of Windows Vista you are using. I suspect that many people with AMD Athlon 64 based PCs (like me) are running the 32-bit version of Vista for driver compatibility. So, just having an Athlon-64 CPU does not mean you should download and try to install the AMD64 version of WMDC.