Activesync is the free application that lets your Windows Mobile device communicate with your desktop. Please be aware that there are three major, not interchangeable versions of Activesync:

• Activesync 3.8 (now depreciated) is intended for devices using the operating system CE2.11, PocketPC2000, PocketPC2002, Windows Mobile 2003 and Windows Mobile 2003SE on a pre-Vista desktop. For newer PocketPC operating systems or newer desktop operating systems, this version will not work at all.
• Activesync 4.x (current) is intended for Windows Mobile 5.0 and beyond on a pre-Vista desktop. Activesync 4.x provides support for older operating systems as well, although on PPC2000 and older the possibility to synchronize e-mail does not work. This version will not install on Windows Vista and beyond. You can download the latest version here.
• Windows Mobile Device Center for Windows Vista (and beyond). This component is included in the Windows Operating system. It will only support Windows Mobile 2003 and beyond. It comes included in the operating system and will be automatically updated if you run automatic updates on your desktop.

Activesync allows you to do the following things:

• synchronize your contacts, appointments and tasks with Outlook. 
• copy files to your mobile device.
• synchronize other applications like time trackers and workout managers

It can do so for more than one device. You can synchronize with two desktops/laptops. By doing so it actually allows you to be used both at home and at work, allowing you to keep both your calendars in sync.

Related Manuals

• Synchronizing through bluetooth
• Copy files from your PC to your mobile device

Troubleshooting

• Troubleshooting version 3.x
• Troubleshooting version 4.x
• Troubleshooting Windows Mobile Device Center