[Macpartners] overheated powerbook g4

[arthur steinberg]

i have a g4 powerbook, running max os x.3.9 that occasionally overheats 
when the power cord is left plugged in over several days.  when i open 
it the screen is dark and i am unable to revive it: i've  tried hitting 
various keys, esc, pressing the on/off button briefly, but it stays 
dark.  i've had to shut it off with the on/off button and once when i 
did this i think i corrupted my address book.

anyway, can someone tell me how to deal with this problem?

thanks.

arthur