You can download Activesync free from Microsoft.
You'll want version 4.2 (or 4.5 beta) if you're running WM5, or version 3.8 if you're running WM2003se (4.x will work, but 3.x is better for non WM5 devices).
4.2 download -
http://www.microsoft.com/windowsmobi...ivesync42.mspx
4.5 download -
http://www.microsoft.com/windowsmobi...ivesync45.mspx
3.8 download -
http://www.hpcfactor.com/ftp-root/so...38/MSASYNC.EXE