I'm assuming you're trying to open your archives.pst file by double-clicking on it? This won't work. To open the file, open Outlook and go to the file menu and select open. Select 'outlook data file' or 'pst personal folders file' (depending on your version of Outlook) and then browse to where you've saved the pst file and open it from there.
Another thing people sometimes have problems with: if you've backed up your pst file to CD-ROM you will need to copy it to your hard drive and then uncheck remove the 'read only' checkbox before opening the file.
Sophia Kelly
www.sophiakelly.ca
Helping People Do Good Things Better