You can manually check for updates for your DivX for Windows products by:
Going to Start > Programs > DivX > Check for Updates > This will launch the DivX Control Panel
You can choose to have the DivX Updater check for updates:
This will cause the DivX Updater to prompt you when there is an update even if you do not have a DivX product running. If you choose never, you will only be prompted for an update when you launch a DivX product.