So I have a MBP 5,1 and a couple of days ago I upgraded the RAM from 2GB to 4GB (this kit) and also upgraded from the stock 250GB 5400rpm to a 320GB 7200rpm (this drive). Every thing is working out good, its faster and more responsive but for some reason it hangs momentarily when I scroll down a web page, which is often, it hangs or sticks very briefly and then resumes scrolling again. It will do it at least once every web page and sometimes 2 or 3 times. It sounds minor but its very aggravating when surfing and scrolling a lot. I use a wireless Logitech Nano VX mouse with one of those fly wheels that spins so pages scroll according to momentum of the spin so I thought that maybe its the mouse but it also does it when I use the 2 finger scroll on the touchpad. So it must be either the hard drive or the RAM.Any thoughts? Also is there an OS X equivalent to memtest86+ and HD Tach, so I can run some diagnostics?