A while back I posted about freezing issues with my Macbook. Thinking back, it may have started happening after I replaced the stock 250GB 54000rpm hard drive with a 500GB 7200rpm hard drive. Could this be causing the machine to lock up because of heat? I do notice it get pretty hot where the hard drive sits. I would try putting the old HD back in, but unfortunately I have exceeded its capacity on my current HD. Just curious if anyone has experienced lock ups because of the 7200rpm HD. This is a Macbook unibody, not a Macbook Pro. Just as a recap, what happens is that it will just lock up. The mouse won't move and the keyboard doesn't respond. It just stops. Once rebooted, it's fine. Does it about once a day at random times. Thanks again guys for any help.