1st - you must enable 'Show hiden files and folders' under Tools/Folder options/View
then navigate to this location:
C:\Documents and Settings\User\Local Settings\Application Data\Identities
here is dir named something like {DC6A84E1-2F28-4EB8-A599-86471F2FFD6C}\Microsoft\Outlook Express
this directory is diferent for every mail account and contains *.bdx files which is what you need
for Outlook useres the path is:
C:\Documents and Settings\User\Local Settings\Application Data\Microsoft\Outlook
and exension of the files is .pst
regards