Have you restored the files? What mail client did you use in XP, oh, Outlook Express 6, I see?
Do you show things like .wab or .pst files anywhere. I am not the expert on where Windows puts it mail folders and such, but I am sure the internet contains that info. It may be in a folder something like this one.
C:\Users\You\AppData\Local\Micorsoft\Outlook
I have not restored any files, so I really can say where it puts them. If you know where they were on your old system, you can probably find them in the restore data base by using the Custom and Advanced settings.
If you have a Windows.old folder or a $Windows.~bt you may still have all the old files from your XP install you could find. Windows 7 doesn't have Outlook Express, as you have probably noticed.
This might give you more info:
OLEXP: How to Back Up the Outlook Express Address Book and Mail Folders