Hi, I have an Asus M51Sn running Vista 32bit and have had this problem for a long time. As soon as I boot up the fan runs almost constantly and the area right of the mouse-pad gets warm to the point that it becomes uncomfortable when working. I sent it back to ASUS last year and I`m convinced they did not nothing with it as it's still the same. It was gone for a month so I'm not going down that road again plus it's out of warranty now.
I did a complete system restore to get rid of adware and speed up my system but this hasn't resolved the overheating issue. As I type this with just Chrome open my CPU usage is below 5%. I have swiched off all start up programs so there is nothing running in the background and it gets hot within a few minutes of startup regardless of what programs are running - I don't game or use heavy programs. I keep the laptop on a flat wooden surface normally and the underside temperature is not a problem. I'm out of ideas! Please, no solutions about wet towels and I know about the coolers but they don't fix the problem.