import email message in Outlook 2003

Just installed Outlook 2003 on Windows XP. Trying to setup users email. All goes well except the importing of email from another machine that had Win95 and outlook express 5.5.
I have copied the correct file from the old machine to the new machine. I use the import/export feature and select import internet mail and addresses. Then I select Outlook 4x,5x,6x. I select the folder that the email messages are in. It gives me the following error “The mail file could not be opened. If another app is using it, close and retry.” This is the only program open. I tried given the user admin rights to the machine but that didn’t help.

Thanks
Edie