Restore OS x 10.5.8 to a few days ago?

Use Time Machine if you have been using it for backups, or else use a regular backup. If no backups then no reverting.

And occasionally data recovery applications can restore data, but they need to be on a bootable disc that will run on your computer*:

http://www.macmaps.com/backup.html

The more your write to your computer, the less the chances you have of restoring anything you delete.

You didn't indicate which MacBook you have. The earliest CoreDuo and CoreSolo models can only run up to 10.6.8.

Later models with Core2Duo can run newer operating systems, with also a caveat, if you ever want to install one of them directly:

http://discussions.apple.com/docs/DOC-6271

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