Archived outlook files will not open on outlook 2010, any suggestions?

I have a new Dell Inspiron 14Z running windows 7 pro 64bit and i'm using Microsoft office 2010.
I'm trying to retrieve archived emails that i backed up on an external hard drive from a previous computer, the files are .pst which is an outlook format but i keep on getting an error message saying the file is not an Outlook data file (.pst).
i dont have any other way to retrieve these emails since they were deleted from the server and its about 1.5 years of work emails. Not sure what to do? should i move the files from the external driver to a different location on the computer and open them, or are they corrupted and need to be fixed?

This might help you: Fix Outlook 2010 Problem: PST File Repair Tool

In short, there's a PST file repair tool included with Office 2010, but no shortcut to the tool exists in the start menu. The above link tells you how to find the tool and run it - see if it can fix up your PST file and make it readable by Outlook 2010.

Thank you Corazon for replying.
i have tried that already already and it still didn't recognize the file. i have also tried stellar Phoenix outlook repair tools and it didn't work. it very strange and frustrating why this file is not recognized.
are there any other suggestions?