Usually if it is a voltage problem the computer won't run. However it is possible it could be. I was just saying that in the normal odds of things, the first thing would be memory going out, specially if it has been runing for a long time. I get that problem and it usually shows up as seg fault errors on linux systems, where the system was running flawlessly for a long time.

About the only way you can tell is to swap parts and see what happens.