This tutorial provides the steps required for hiding the choose profile window that gets displayed when starting Outlook 2010. The profile window is displayed even after specifying the default profile using the Options button.
One of the common cause of this problem is said to be the installation of Google Apps Sync tool on your Windows system.
To hide the choose profile window, navigate to Control Panel –> Mail options.
Click the Show Profiles button available under Profiles section.
Now select your preferred profile and click the radio option with label as Always use this profile. Click Ok to confirm and save the changes.