The first thing I would do is see if his Outlook Express storage files are still there. On Windows NT/2K/XP, the path is
C:\Documents and Settings\USERNAME\Local Settings\Application Data\Identities\{GUID}\Microsoft\Outlook Express
and on a Windows 9X/Me the path is, if I remember correctly, is
C:\Windows\Application Data\Identities\{GUID}\Microsoft\Outlook Express
and then back everything up before you go further. He may have several OE storage folders on his hard drive. While he is there, have him check the sizes of the INBOX.DBX file(s). If it is small (~59KB) then it is probably empty. If the file(s) is >59KB then his email is likely intact and then you can proceed on a method of retrieval. Your friend can see what his current storage folder in OE6 is by clicking on TOOLS > OPTIONS > MAINTENANCE and then clicking on the STORE FOLDER button. What was his previous OE version anyway?