This is a great tip I found last week on The Unofficial Apple Weblog about how to do clean install of Snow Leopard if you ever really need to do it. This is also handy when you are selling your machine and want to restore it to its original settings while getting all your personal info erased from your iMac or MacBook:

What I wanted to do was to do the ol’ ‘erase and install’ that prior system software discs allowed you to do. But clicking around Snow Leopard left no obvious method for this. But instead of booting Snow Leopard while inside of Mac OS X, if you just directly reboot the computer off the disc itself (holding down the ‘c’ button after the system chime, letting go when you see the Apple logo) you get a few more options. Once you’ve gone into the installer program, you’ll see ‘Utilities’ at the top, and if you select Disc Utility, you can see your hard drive. If you click on ‘erase’ (like I did, with one hand over my eyes) you can wipe the drive clean with various security options, and then you can do a fresh install of Snow Leopard on your computer on a pristine hard drive.

Once you’ve done that, you can either transfer your files back in directly, or use the installer program’s built-in migration utility to restore any or all files from Time Machine.

(Via The Unofficial Apple Weblog (TUAW).)