If you receive an error message relating to an invalid or missing .DLL file when installing ActiveSync, you may need to upgrade the version of the Windows Installer running on your PC.
Windows Installer 3.1 can be downloaded free of charge from the Microsoft web site:
http://www.microsoft.com/downloads/details.aspx?FamilyID=889482FC-5F56-4A38-B838-DE776FD4138C&displaylang=en
NOTE - you will need to validate your copy of Windows before downloading the file.
James Liddiard
Network Manager