Need advice on How to Restore Apple Mail

[gregondera]

Lately my Mac dual 3.2 Ghz Quad-Core is restarting on its own when it is cold a number of times. I was right at the start of opening my Apple Mail application when it restarted on me. When I opened Mail the next time, it only showed an account I was not familiar with: a "me.com" account and 68 emails, all from Apple. But my 7 other email accounts are all gone, not there! They are not in preferences in Mail. I can see the folders in Users>Library>Mail but don't want to screw anything up trying to get them back. I checked my mail on my iPhone, but need to restore this computer Mail program. How do I do that without wiping anything out? I am on OS 10.5.8 and I'd like to get all the old emails back, the accounts back in preferences too. Thanks!