Problem with OS X Mail

Hello,
I have been using the Mail client that comes with OS X for quite a while now, and until today it all went well actually.
I just opened my mail client and it asked me to set everything up again from scratch.
I checked in library in my user folder, and all the mail files are still there... and probably also all my email. The problem is that I cannot open them unless I re-enter all my data into the mail client. HOweve, I am a bit reluctant to do that, because I am scared that if I enter a new accout with the same details as I had before, that all my mails that are still in library will be overwritten.
Does anyone know how to see all my emails and all in my mail client again without having to set up a new accout?

Thanks,
lilbird.

Ooh, scary. Just in time for holloween.

Copy these folders to the desktop as backups:
~/Library/Mail/
~/Library/Mail Downloads/ (if present)

Now in case your current messages get overwritten, you can copy your backup from the desktop to restore your message.

scary indeed... I will try that later when I'm back on my mac.

Thanks!!
Jenny.