open your Outlook Express.
click on 'FILES' select 'IMPORTS AND EXPORTS'
select"EXPORT TO A FILE" & hit 'NEXT'
select 'Personal Folder File'(.pst) & hit 'NEXT'
select the folder that you want to save like if u want to save 'inbox' emails, select that and type 'inbox.pst' & hit 'NEXT'
you need to know where to put that files; however, if you have cd or dvd burner, you can put the files onto cd before you would format a hdd.
after reinstalling your xp, you can go back Outlook Express to select 'FILES' and select 'IMPORT FROM ANOTHER PROGRAM OR FILES' & hit 'NEXT'
select 'PERSONAL FOLDER FILE (.PST) & hit 'NEXT'
you need to browse the file to cd (if you burn the files to cd or dvd) & hit 'NEXT' that would put all files such as inbox.pst back to outlook.
if you want to save contacts, you can save it as 'CONTACT.PST' and you can put them back as you follow this instruction.
good luck...