Outlook 2003 .pst files in Windows 7

I am having a lot of problems setting up my Outlook 2003 on a Windows
7 computer. When I first got the computer I set it up correctly, but I
had to return the computer to the manufacturer for a new motherboard
and they wiped the hard drive without telling me first. Luckily I had
a backup of the drive on an external hard drive.

I installed the Outlook 2003 program and connected to the Internet and
all the emails that had been sent to me when I did not have the
computer were downloaded into the Inbox. I then copied the saved .pst
file and went to File/Open/Outlook Data file and pasted it there while
I was offline. I have had to do this a few times as this data file
seems to disappear periodically.

Now I have three Personal Folders. The first one has all the normal
Outlook folders: Inbox, Unread Mail, Sent Items, and so forth. It has
no file folders, except for one which I experimented with and copied
from my second Personal Folders and pasted there. Incoming mail comes
to the first Personal Folder Inbox.

The second Personal Folders is empty and when I hit it I get this
message: "Unable to expand the folder. The set of folders could not be
opened." I cannot even delete this folder because I get this message.

The third Personal Folders has all the normal Outlook folders--its
Inbox has the emails that were there when I originally backed it up--
and all my file folders. I have added emails from the first Personal
Folders Inbox to these folders. I also have a link to this Personal
Folder of my Contacts, Calendar, and Tasks. When I write an email,
since all processes are attached to the First Personal Folder, the
address is not automatically added.

How do I get all folders, files, and functions under one Personal
Folder? I hope that the above is clear and explains what I have done
so far.

Thank you for helping me. I am becoming desperate!

Caryl.