I recently downloaded and upgraded to OSX 10.8. In hindsight, I realized I should have done a clean install. Is there any way to reinstall OSX 10.8 as a clean install?
Before doing /anything/, make a backup of everything in case something goes wrong.
Download OS X from the App Store by holding option and clicking download. Close the installer when it finishes downloading and automatically launches. (You'll have to secondary-click the dock icon for Installer and quit it)
Download LionDiskMaker (liondiskmaker.com) and run that. You'll need an 8GB USB Flash Drive.
Once it finishes, shut down your Mac and boot it back up while holding the Option (alt) key, then select your flashdrive from the list of bootable drives.
Open Disk Utility once the interface comes up. Select your drive and format it. (DO NOT DO THIS IF YOU HAVE NOT RUN A BACKUP. It will delete EVERYTHING on your drive!)
Once that's over, close Disk Utility (CMD + Q) and run the installer.
Yes, and I did it on a Macbook Air. You need to download OS X from the App store, then follow any guide for creating a bootable setup drive, such as this one. Then you must restart your Mac and boot from the drive you just created, and run a setup of OS X. During the setup, make sure you erease the content of Macintosh HD with Disk Utility.
I suggest you make a backup of your system with Time Machine before attempting a clean install.