To be specific, I have an older Samsung SGH-D600 slide phone.

The power switch works even with the slide shut. So it often accidentally turns on when carried around. It doesn't matter that the pin has not been entered, the battery runs down if I don't notice and don't use the phone for some time.

Is there any way of disabling the power button when the slide is shut?

The instruction manual says to open the slide to turn on the phone. So I don't know if this is actually a hardware / software problem?