Solid Hardwood, Engineered and Laminate Flooring - Underpad problem

i just bought a house and ripped up the carpets. the carpet under pad is still sticking to the plywood. i want to install laminate flooring which comes with a underlayment pad already glued to each board. can i lay this laminate floor ing over the existing under pad or should i lay down quarter inch plywood for a new surface. the old carpet under pad will not come up easily and is crumbling. any advice would be appreciated. thanks

You can rent a sander which would help in removing this underpad. Ideally, the existing underlay should be removed.

If it is what I think it is, put some old tennis shoes on and shuffle across the old deteriorated padding, slide your feet and it will rub it off enough to install your flooring.

Ah, the high tech way. :)

I'm thinking it is really old rebond. When it was first made it had no skin on the surface. Some full spread it down so it wouldn't bunch up under the carpet trying to position the carpet, during installation.

The stuff just crumbles, and must be hauled out in trash bags instead of just rolling it up.