>Also verify that the laptop isn't getting abnormally hot. If a fan is dead or blocked you could have an overheating problem.
>

Thank you both Al & William. He went into some repair shop yesterday and they detected a bad hard drive and said they are going to replace it for $400 (250 for 80GB drive and $150 for work). Sounds like too expansive to us, so we may want to try your advices first.