I have an old black MB 2.16 ghz C2D. At times, it locks up and randomly reboots. Sometimes, it gets crazy and reboots again after its done booting up. Sometimes, I get this gray screen that says I have to hold the power button as well. I don't really notice the laptop getting warm at all or the fans turning on that much. I just reinstalled the entire OS and Snow Leopard. I just got a new MBP, so I haven't really been using that one as much (or at all). So, it's hard to say if that fixed it. My applecare runs out on 5/29/2010. And if it's a hardware problem, I'd like to get it fixed prior to my warranty expiring. Any ideas? Thanks!