none of my screwdrivers are thin enough to fit in the top holes
i don't know what that means.
get yourself a torx T15 screwdriver or extension that's at least 6 inches long. should sell them at home depot or whatever
tbh, your post is really "i have tried nothing and i'm out of ideas".
its a 35 year old computer, you gotta crack it open and inspect for faults
realistically it's probably just the memory.