My powerbook G4 17 inch is getting more and more unusable.
If I watch a movie on it the machine stops working after a half an hour off watching.
Guess it's a heat problem as the bottom gets very hot, especially the battery and the left side(processor?)
The fan is blowing now and then so they do work maybe thermal paste?
Also the wifi connection through a pcmcia card isn't always there at bootup.
Have to do a reset to get it going.

What would be the most reliable laptop for mos,given heat,batterylife.

Thermal paste has dried. Get some Artic Silver or something like that and replace the thermal paste. Also clean the fans.

http://www.ifixit.com/Guide/PowerBook+G4+Aluminum+17-Inch+1-1.67+GHz+Heat+Sink+%26+Fan+Assembly+Replacement/259

It is not unusual to see 15°C to 25°C temperature drop after such maintenance.

Ok thanks for advice.
I'll try that.

If the battery is getting hot even though the laptop should not be charging, it could point to a faulty battery or the AC board.