Powerbook dead? Sleeping? Playing games with me? Please help!

Question

Please advise me about what to do with my 15" aluminum G4 1.25 GHz Powerbook. Often it won't start at all, and if it does, soon it freezes solid (screen still up, but no response to the trackpad or the keyboard) and I have to force it to quit or remove the battery. Meanwhile the bottom of the case quickly feels very, very hot, even if the screen is (sometimes) blank. Yesterday I got it to run long enough to run the hardware test, which passed the logic board and other components -- before the computer froze up again. A Mac-certified tech looked at it and said he thought it needed a new logic board; but would it have passed the hardware test if that were the case? I've tried resetting PRAM, removing RAM, the airport card, etc., and I just can't see any consistent result, except that whatever I do, the laptop will soon freeze up. I've read about the famous "narcolepsy" issue, but if the laptop is going into emergency sleep mode, would the screen still be working (if frozen)? I really am just about ready to call it quits and sell this for parts. I'd be grateful for advice. Thanks.

Answer 1

BGregg and Old imac, thanks for your comments. I tried to reply once to this but my post got lost in the ether, I guess. I believe my hard disk is okay and since I wiped it and reinstalled Leopard, that can't be the problem, I think (not much on it now except the OS, I mean).
But good news!!! I did the following things and the laptop has now been running non stop for 4 hours! Hooray! (1) removed ram from upper bank and only have ram now in lower bank (1 gig); (2) have not touched the track pad at all -- am using an external mouse. Have touched the space bar a few times to wake it up from sleep; (3) installed and am running Temperature Monitor. Now this is neat: when I first installed it, it showed temperatures around the CPU mounting up to 140 - 145 degrees F !!! Since then, however, it has been running much, MUCH cooler, around 100 F. Could the Temperature Monitor program be responsible for this cooler-running machine? Anyway, I don't know which of these three things I changed is responsible for the machine continuing to run properly for such a long time (compared to its recent history). Which should I try changing first? RAM or using the track pad? I guess it doesn't make much difference. Suggestions?