How to restore back to factory settings after upgrading to Snow Leopard?

[YsoSerious]

I upgraded my Mac from Leopard to Snow and want to do a complete reinstall erasing all data on it and restoring it back to factory settings.

 

[ziggyonice]

If you want to restore your Mac to it's original condition (i.e. before Snow Leopard, without any application updates whatsoever, like you originally received it) you need to use the discs that came with the computer. Perform an "erase and install", erasing the computer and installing Mac OS X and your Mac's included applications.