Outlook Reminders Don't Sound When Windows is Locked



We recently upgraded several of our users from Windows XP, Office 2003 to Windows 7 64 bit, Office 2010. Now Outlook reminder sounds do not play when Windows is locked. We force our systems to lock after 15 minutes, so people are not happy when they miss appointments because they are not actively using their computers. How can we force reminders to play even when the system is locked?