Yes. Our software utilizes Microsoft's Volume Shadow Copy Service (VSS) to back up open and locked files. If you select (.pst) files in a File and Folder backup set, the software will back up those files even if Outlook is open. You need a version of Windows that supports Volume Shadow Copies and an NTFS-formatted hard drive for shadow copies to work. Windows XP, Server 2003, or any later version of Windows all support shadow copies. Keep in mind large (.pst) files may require a large amount of drive space allocated to shadow copy storage to successfully create shadow copies. If there is not enough free drive space or the space allocated to shadow copies is too small, VSS will not be able to create its snapshot and the backup job may not be able to back up those files which are in use or locked.