If you didn't back them up they are probably gone for good, since the
default storage location is in a sub-folder under Windows. But try this:
If you were using OE 5 or higher before, search your hard drive for
Inbox.dbx
(If you are using Win2K or WinXP you will have to set the search to include
hidden files and folders.)
If you find two copies, use OE's File | Import | Messages | Microsoft
Outlook Express 6 and choose to import from an OE6 store directory. Browse
to the folder holding the older Inbox.dbx.