Hi, I have an early 2008 MBP (MacBookPro4,1 model) with 2.4 core 2 duo processor and 4GB of RAM. I upgraded to Lion when it came out, about a year ago, and my computer has been very slow ever since. It takes forever to boot, and then it does not run smoothly as it used to do with Snow Leopard. Programs lag to launch and things are slow in general. Is there anything I can do, short of going back to SL, to improve performance? When I upgraded I did not do a clean install. Does that make a difference? Thanks!