If you are using Windows look in:
windows\application data\identities and look through each of the SID numbers to find your old files. The address book will be found under microsoft\address book instead of identities - files ending wab.
In NT you will find same in winnt\profiles\username\application data as before
You should be able to copy or import these to your current identity (create a local folder and find it in one of the identities to see who you are!)
make sure run the express utility to backup your emails to another directory or
To back up the folder, find the folder file, and then copy it to a backup folder, floppy disk, or network drive. Outlook Express mail folders have a .dbx extension (for example, "Sent Items.dbx").
Notes
good luck