However, the Snow Leopard upgrade DVD does not require that you have Leopard installed; it's a full install disc that works on any Intel Mac.and another from MacInTouch:
Can I install the Snow Leopard upgrade on a blank hard disk?While this may be true of the retail upgrade disc, bundled DVDs and those issued under the Mac OS X Snow Leopard Up-to-Date Program (distinguishable by the notice "This software is part of a hardware bundle - not to be sold separately") do not work on older Macs with blank drives, as this screenshot demonstrates:
Yes. According to a number of reports, you can even install it on a Mac that does not have a Leopard disk attached.
For bots, screen readers, and image-free browsers, here it is in plain text:
Mac OS X can't be installed on this computer. This disc requires that Mac OS X 10.5 or later already be installed on your computer. If you want to restore your system from a Time Machine backup, click "Restore from Backup".The only choices are "Restore from Backup" and "Restart". Not even the usual utilities (Terminal, Disk Utility, etc) are available. This message can be avoided by plugging in an external drive with Leopard installed (including another Mac in Target Disk Mode) or by remastering the DVD with a few minor changes. For more on this issue, see:
/mac | Dec 14, 2009