Perhaps silly questions for those of you with the 'can't find serial number' problem:
a. Did you buy the qualifying Mac from an Apple Store (either online or bricks & mortar) or an Apple Authorized Reseller?
b. Did you register your purchase with Apple, either during the initial setup or via the
Apple Product Registration page?
c. Is your new Mac listed on the
Snow Leopard Up-to-Date New Macs page, or your refurbished Mac on the
Snow Leopard Up-to-Date - Refurbished Macs page?
d. On the qualifying form, is any field name
besides the serial number you entered marked in red when you click on the "Qualify System" button & get the "Sorry, we can't find the serial number you provided" error?