Hi. I'm considering doing the regular, "easier" install of Yosemite. However, my comp is a bit on the older side (iMac 2.66 Core duo purchased in '09, 4G RAM). A clean install will probably result in a faster computer, but is a bit more complicated to do, what with having to reinstall all my programs and such. If I do the regular install method, and find my computer is just too slow, can I do a clean install after that? Or do I just have one shot to do the upgrade, and that's it? Thanks.