Outlook Express 6 – blank inbox, 500MB

We have Windows 98 with Outlook Express 6. We started getting errors when trying to check email: msimn caused a ipf in module directdb.dll. After reopening the program, it said the inbox folder could not be opened due to low memory or disk space. The hard drive has 20GB free and the computer has 128 MB RAM. From internet research, I renamed the folders.dbx file to folders.old. Now, the program works great, but the inbox folder is completely empty of the 300 messages it had before I renamed the folders file. All the other folders still have all their emails intact. Only the inbox folder is empty. Help, is it possible to restore? I did not delete any files, only renamed the one. The inbox.dbx file is 488MB. Something’s gotta be in there, right?