Need some help restoring mail for Mail.app

Hey all, my mom's iMac was having some seriously serious software issues (Aperture was über slow, which I hear is actually a feature. ) and Mail.app's accounts were all messed up. They wouldn't send e-mail, wouldn't' receive, etc.

So, we backed everything up, zeroed the disk, and installed Leopard. I then entered all her account info manually and things are working like a charm (even Aperture's special feature has been semi-disabled). Unfortunately, she has e-mails going back three years and needs to recover all the ones she sent and saved. I am reluctant to simply restore the accounts because then whatever bad preference we had last time will simply migrate over.
Is there a way to drag over her old e-mails manually?

Thanks.