I apologize if this question is somewhat basic, but I could really use the help. I recently upgraded my MacBook Pro 13" (mid 2011) from Snow Leopard (I believe) to Mavericks. Although many new features work really well, I have never experienced any laptop or desktop run more slowly since the days of dial up. I have plent of space (nearly 100GB) left on my hard drive and the only new installation lately has been Mavericks. However, simple tasks like opening a Youtube video now take 3x as long. Any advice on how to find the source of the problem or speed my computer up a bit? Thanks a lot!