MBP mid-2009 15", 2.53ghz, 8GB Ram I replaced the factory hard drive today with a Western Digital Scorpio Black 500GB 7200 RPM drive. Before I installed it I used Carbon Copy Cloner to clone the drive and then I put the new one in. As expected it took a few moments to find the drive (searching for startup drive), and then it booted. From that point on, everything was lagging and whenever I clicked on anything I would get the spinning beachball. I tried resetting the pram and power settings, and repaired all the permissions. I changed the startup disk to the new disk under sys prefs. With all that, the extreme lag persisted. I put the old drive back in and everything worked fine. Any ideas?