Hello all I currently have a Mid 2009 MBP 15" A1286. Running 2.53ghz, 8gb ram and the original hard drive. I am running 10.6.8(Snow Leopard). I'm wanting to upgrade my hard drive to a solid state drive(256gb). For the quicker performance, cooler machine, etc etc. And I want to upgrade my OS to Yosemite. According to all the forums, my machine will be ok with the OS upgrade. Reason for the OS upgrade, is, I am starting to notice a serious lag, with Safari and/or Firefox. Seems the newest release of Firefox, does not like my Snow Leopard very much. Pages seem to hang and I am constantly refreshing pages during the loading phase, to get them to even open. My sister has a MBP as well, a 2013 with Mavericks, and her internet streaming, off the same connection, is waaaaay better and she does not have the hang ups or lagging. Her system, is also running a smaller processor, though it is an i5. I am hoping the upgrade of an SSD and operating system, will help and also help to avoid having to buy a new MBP, for a little while longer. Any help or ideas would be appreciated. Thanks!!