Hi all, I have already upgraded from mountain lion to mavericks through the Mac App Store. If I would like to perform a clean install can I still do this although I have gone through the upgrade process? In other words is the mavericks upgrade app still on my computer somewhere? Many thanks, Nubben
Unless you saved the installer to a different place other than the Applications folder, you will need to download the installer again, before you can create a bootable USB installer.
Unless you just want to DL Mavs to make the USB key, there is no need to download it from the app store and mess with the USB key. Since you have already installed Mavs, you now have a Mavs recovery partition that can be used to install Mavs directly. So just command-r boot to recovery. Use Disk Util to erase Macintosh HD, then click install OS. You will be asked for the AppleID you used to get Mavs from the App Store. This will give you a clean install without the use of the USB key.