One of the bad things about old PowerBooks is that sometimes the screws were installed a little too tight, either by the factory or an overzealous repair person. This can lead to two conditions: broken screw mounts, and seized screws.
WD-40 would probably be the best bet for trying to get those screws out. If I were you, I would grab a box of Q-tips. Then, I'd take one of the Q-tips, soak one end in WD-40, and dip it into each screw hole. Maybe spin it around some in there, and resoak it for each screw.
Then, I'd let it sit for half an hour before I went in there and tried to extract the screws. Assuming this works, I would then remove the screws and take a dry Q-tip to each hole and attempt to soak up as much WD-40 as possible.
This may need to be done on some of the interior screws, as well. Be careful near the logic board. Make sure to clean up any excess WD-40, particularly near ESD-sensitive devices.
On reassembly, I would then install the screws to the point that they are snug, but not really tight. The plastic on those things is often quite brittle by now.
There really isn't a risk of explosion from WD-40, so long as you remove the battery and power adapter before you start spraying that junk willy-nilly. That warning is there mostly so people don't spray it in live light switches or electric motors or other such things.
Good luck!
WD-40 would probably be the best bet for trying to get those screws out. If I were you, I would grab a box of Q-tips. Then, I'd take one of the Q-tips, soak one end in WD-40, and dip it into each screw hole. Maybe spin it around some in there, and resoak it for each screw.
Then, I'd let it sit for half an hour before I went in there and tried to extract the screws. Assuming this works, I would then remove the screws and take a dry Q-tip to each hole and attempt to soak up as much WD-40 as possible.
This may need to be done on some of the interior screws, as well. Be careful near the logic board. Make sure to clean up any excess WD-40, particularly near ESD-sensitive devices.
On reassembly, I would then install the screws to the point that they are snug, but not really tight. The plastic on those things is often quite brittle by now.
There really isn't a risk of explosion from WD-40, so long as you remove the battery and power adapter before you start spraying that junk willy-nilly. That warning is there mostly so people don't spray it in live light switches or electric motors or other such things.
Good luck!