Hi and welcome to JustAnswer.com. My name is Nick and I will assist you with your issues.So you would like to upgrade Outlook 2003 to 2010?
You should always create backups of the .pst files in Outlook even if you aren't upgrading to a new version. That said, create a back-up of each user's .pst file/s and then do your upgrade to Outlook 2010. You should not have any issues
Here is the link for reference the differences and new features of Outlook 2010
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