They squeak loud enough to wake the dead. If you have access to the floor from the basement below, then you can attack your squeaks. You need to be very careful that the screw doesn't go through the underlayment and poke out the vinyl. But this is probably the best fix since you can pull all the layers down tight against each other. Floors squeak I have a 2-yr.
Joists are solid wood.
Floors are PLY and glued to the joists. You better check out the other structure aspects of your house, because chances are the poor quality continues in other areas of your house. My first house was like the one you describe. The second level floors of my home squeak. I'm sure the builder failed to include glue.