So Outlook 2003 and 2007 store the email account details there.

Which you need to know BEFORE you rebuild your PC.  (So you can take a backup copy of it).

Not that obvious until you need to know where to find it: HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles\Outlook\9375CFF0413111d3B88A00104B2A6676

Microsoft commits to releasing Outlook PST format

This is big news, particularly if you’ve ever tried to convert an OST file to a PST file.

… In order to facilitate interoperability and enable customers and vendors to access the data in .pst files on a variety of platforms, we will be releasing documentation for the .pst file format.  This will allow [...]

How to convert an OST file to a PST file

(if you don’t know what an OST file is, see below)

There are four options, one of these below might work for you. NOTE: This is a work in progress post.  It will be updated when I learn something.

The OST2PST conversation method.

Backup ost file(s) Rename outlook.ost to outlook.pst Use scanpst.exe from Outlook [...]