Excuse the rant but: A normal Mac user does not need to do a clean installation of Mavericks. Indeed, for many inexperienced users it's a risky process since it involves erasing your computer's hard drive and starting over. That necessarily entails added risk. I would say that even if you have a working TM backup it's a bad idea; do you know that TM backup is good? And if AFTER the clean install you use setup assistant or migration assistant, then you're probably not doing a really "clean" installation, since you have no idea what those processes are choosing to migrate over. It'll probably just replace ALL the non-system stuff you just erased. And if you don't know the difference between those two methods -- setup and migration -- that's another reason you shouldn't do a clean install. Hint: user ID number. And you can't manually install from TM in any reasonable way. Manually installing all your applications and settings can be a real PITA. And unless you have a very simple setup (ie mostly Apple or MAS applications, and saved copies of all your downloaded software) moving things manually can break stuff. And if your setup is simple, than what's the use of a clean install? And if you have a clone and/or another good backup why not try a regular, Apple-sanctioned installation of Mavericks? It's faster, simpler, and at least as likely to be successful as erasing all your stuff and starting over. And if it doesn't work for some reason, THEN you can do your clean installation. You only lose a little time this way at worst and at best you save a ton of time. Finally, what's the rationale? Are you seriously worried about superfluous 512k pref files on a one terabyte drive? I can certainly see it if your current installation is wonky, but better to diagnose the problem. Almost all of us are just fine with Apple's way of doing an upgrade. There is simply no need to do a clean installation of the new OS unless you have a specialized situation (say you don't have a Recovery Partition and now want one). Do yourself a favor and at least TRY Apple's method first. You probably will save yourself a lot of headaches. I want you to be successful; I really do.