I have a 2011 mbp 17 inch, and I only have starcraft downloaded and a couple of movie files. I have had it for about 6months now, and was wondering if I should do a fresh install of lion. I don't want my computer to slow down " even a couple of seconds" and im afraid that will happen if I don't do a clean install. could someone advise me what to do, also could someone post a link of how to do a fresh install properly. " also with a fresh install will I have to reinstall snow leopard then lion?"