Outlook PST File Problem

I have transferred to a new computer and archived all of my outlook information into a file (1.5GB). When I try to open the pst file in outlook it tells me that it is not a personal folder file, I have a lot of information that I would like to get out of it.

I have tried the pst repair tool but once it has been through thta it leaves me with about 3 emails and nothing else.

Thanks