What is causing my laptop to overheat?

My HP nc6400 laptop has had a rough few months.  As mentioned in two previous questions, I have experienced some BSOD errors.  Speedfan has also clocked the computer randomly hitting 80 degrees (C) when not doing any intensive work nor running more applications than usual.

I'd suddenly notice that the fan is revving (yes, it is running, and dust is cleared), and I look down at my taskbar (running XP) and notice a crazy high temperature.  I usually take immediate steps to hibernate or otherwise power down my computer.

Just today, after not having problems for more than a week, I noticed that Speedfan clocked my CPU temp at 91 degrees (C).  Knowing that this would very well fry an egg, I took immediate steps to save whatever I could and power down the computer.

I have a ticket into HP to ship back my laptop (box is sitting next to me) to fix both a bad LCD screen (line down the screen) and investigate the overheating problem.  However, I use my laptop anywhere from 40-80 hours a week (consistently using the same programs, and shutting down each night), and it only overheats maybe once a week.  Thus, they're likely to "investigate" the problem, find nothing wrong, and ship me back my computer as-is.

I don't want that.  Is there anything I can do to track down this issue before I ship it out, or should I just push HP really hard to make sure they replace some or all of the motherboard-cpu-fan-heatsink components?

Somewhat related questions: http:Q_23541666.html and http:Q_23501454.html

Thanks,
Andrew