MacBook hangs or freezes frequently
My Macbook frequently hangs or freezes. Generally, have the spinning color wheel and sometimes just the mouse pointer. Control tab doesn't work or does after a long delay. It's acting like it's really busy doing something. Activity monitor shows some apps are not responding, which app varies from time to time. If I wait long enough...hours...it will sometimes recover. The sure fire fix is to hard reboot. It has 4gb of RAM and I replaced the hard drive with a 1TB hard disk after I bought it about a year ago. I have little history on the computer as I bought it used from a college professor with a dead disk off Craigslist. I don't use Safari, and generally am using Chrome.