i've had my M1530 for around 20 months and up until 4/5 months ago it used to get rediculously hot under every day usage because the air hole is right where your thigh goes when you have it on your "lap top"
i bought a Belkin Cushtop - a light, firm cushion, and it raises the laptop off your lap so air can get around the base. it solved the problem of it setting fire to my legs!!
however the other night i was watching a film on my TV via HDMI cable, and half an hour in, the laptop just went off - i thought maybe the cord had been pulled and the battery had gone flat - but when i went to pick it up, it was absolutely boiling, all over its case - i think it was very close to catching fire or burning a hole in the cushtop, i've never felt it that hot before.
I dont know what the reason was, since i've watched plenty of films before in the same way.
I have just got a new battery as the original one stopped holding its charge a few weeks back - and i went for the 9-cell - and i think this will help even further with the problem since the battery doubles up as a riser for the back of tha laptop - theres enough space under the back of the laptop to get 3 fingers under [fingers flat across the bottom of hte case]
also i have a 4.5 hours battery life instead of 35 minutes which is an improvement!