While the standard OS is "keyless," there are two specific scenarios where you might go hunting for a number:
: If you want a fresh start, use Disk Utility from the "Utilities" menu to erase your drive (format as Mac OS Extended Journaled ) before installing. Do I Need A Serial Number To Install Snow Leopard
: Occasionally, if you call Apple Support to order replacement recovery discs, they will ask for your Mac's hardware serial number (found on the bottom of the machine or under "About This Mac") to ensure they send the correct version for your specific model. Why People Get Confused The confusion often stems from two places: While the standard OS is "keyless," there are
: Insert your disc, restart your Mac, and hold the C key (or Option key) until the boot menu appears. While the standard OS is "keyless