How can I restore my archived MS OUTLOOK data file to my reformated hard drive?

Copy the archived MS Outlook data file to the folder \Documents and Settings\(username)\Local Settings\Application Data\Microsoft\Outlook and you will find it when you open MS Outlook. Thesr are other ways too to restore but this the coolest one

That depends upon how you've taken backup. Normally you have to take backup from the path something like it,

'C:\Documents and Settings\administrator\Local Settings\Application Data\Identities

\{75A60E94-F5F9-4FF7-B435-17C5ABAD63D8}

\Microsoft\Outlook Express'

After reformatting you have to install MS Outlook you will get that its inbox,outbox and other folders will be kept in a path some thing mentioned above. You have replace those file with your previously taken backup file.