How to Import an OST File in Microsoft Outlookby Bennett Gavrish
The Microsoft Outlook application automatically creates an OST file, or offline folder file, when you initially configure the program to connect to an email account. A copy of your mailbox is stored in the OST file, so that you can access your mail even if you are not connected to the Internet. OST files are always stored in the same location, so you can import an alternate OST file by placing it in the proper location.
Make sure the Microsoft Outlook application is closed and not running.
Open the Start menu and click on the \"My Computer\" icon.
Navigate to the C:\\Documents and Settings\\username\\Local Settings\\Application Data\\Microsoft\\Outlook directory if you are using Windows XP. Windows Vista and 7 users need to navigate to the C:\\User\\username\\Local Settings\\Application Data\\Microsoft\\Outlook directory.
Find the file named \"Outlook.ost\" in the \"Outlook directory.\"
Drag-and-drop the \"Outlook.ost\" file to your desktop.
Copy the alternate OST file into the \"Outlook\" directory.
Rename the alternate OST file to \"Outlook.ost.\"
Open the Outlook application. Outlook will now automatically import the new OST data and treat it as the primary OST file.