I have a 15' Macbook Pro from 2006, with a 2 ghz Core Duo processor, 1 gb of RAM, and an 80 gb hard drive. Throughout the past few months it has become more and more unreliable: the screen completely locks up, requiring a full hard restart, at arbitrary times throughout the day, and this happens with increasing regularity (it started doing it about once a week; then it increased to about once a day; now it usually does it a few times per day). These crashes do not appear to be tied to temperature or intensity of use, and they happen both on the battery and on regular power. Sometimes, but not always, they are preceded by a half an hour or so by arbitrarily placed, 1 pixel wide green horizontal lines appearing on the screen. I thought it might be a software issue, so I wiped the hard drive clean and started with a fresh copy of 10.6, but the problem persists as before. Thus, my questions are these: 1. What hardware component is most likely at fault? 2. Is there a place where I can purchase a reasonably priced replacement? (I'm fine installing it myself.) Or is the computer irreparably on its last leg? It works perfectly in all other respects, and I'd like to continue using it for another couple of years if this problem can be solved for significantly under the cost of buying a new one.