If you did a system restore then the folders containing the e-mails may heve been overwritten by the restore files.
Search your computer for files ending .dbx. These are your emails. There should be Inbox.dbx, Outbox.dbx, Drafts.dbx etc. There must also be Folders.dbx, this is the data telling OE how the emails are compressed. Save all these dbx files, then you can either import them into OE,