Trying to import mailboxes from old computer without sucess

[jss273nyc]

I'm trying to import mailboxes from my old mac but am having some problems. First, the mailboxes I'm importing were mailboxes that were previously imported from Outlook Express into the previous version of Mail 1.x. When I was using Mail 1.x I was able to import these no problem. They showed up in a folder entitled Imported. I'm now on Tiger and using Mail 2.x. on a different computer. I cannot get my application to recognize the imported mbox's that were previously on my old mac. Everytime I try to import them, the program says that there are no recognizable mbox's. Can anyone help? Thanks!