Technically, you restore from your Mac's original restoration media (either DVD or USB stick). If it was Snow Leopard, then go to the App Store and download the

Technically, you restore from your Mac's original restoration media (either DVD or USB stick). If it was Snow Leopard, then go to the App Store and download the Lion update again for free because it remembers you bought it before. I assume Apple will sell a DVD version for MUCH more money (full $129 or higher) that you can use to do a fresh install or upgrade from Tiger and Leopard. I also assume the Lion upgrade in the App Store will be super cheap. Probably $30. Possibly as cheap as $10.