You can also Buy lion from the app store and put it on a usb flash drive to install later That is what i did on my macbook and then you also can do a clean install but its a big download (Over 4GB) it took 3 hours for me to download it so get ready to wait. http://osxdaily.com/2011/07/08/make-a-bootable-mac-os-x-10-7-lion-installer-from-a-usb-flash-drive/ I wonder if Apple Will still keep Lion on the app store once ML comes out?