Pop-up reminders are a nice feature of calendar appointments in Outlook 2010. By default, appointment reminders pop-up 15 minutes prior to the start of an appointment. For me, this normally isn’t enough time so let’s review how to change the default to a more reasonable time.
Open Outlook 2010 and Click File >> Options
Click the Calendar Tab and under Calendar options, adjust the default reminders from 15 minutes to your desired time.
I hate being late for appoints which is why I personally set 1 hour as my default on all Outlook installs.