In our living room in front of the entrance door, there is a piece of plywood (6 ft x 3 ft) glued down on top of the hardwood floors. (I think it's plywood, maybe it's particle board). Anyway, this plywood serves as a substrate for linoleum tiles. I imagine the previous owners put the plywood to lift the tiles to the same level as the wall-to-wall carpeting which they covered the hardwood floors with. We're restoring the hardwood floors and have removed the wall-to-wall carpeting, but now we have to figure out a way to remove the tiled plywood substrate (the tiles are so old, they slide right off). It appears to be glued instead of nailed. Any suggestions on how I can remove it without damaging the hardwood floor underneath?

Thanks in advance for any advice!

Slow an easy while trying to pry it off the hardwood. You;ll be lucky if the old glue has crystalized and the wood pops off easily. I would try sanding the top of the plywood to see if you can find buried nails or screws first.

Thanks for your reply floormeintucson.

Unfortunately, I've already tried to slowly pry it up with a wonder bar and that thing seems well fused, lots of tearing and cracking going on when I try. I think they may have used wood glue. At any rate, I'm pretty sure it's not coming off in once piece.
Can I chisel away the bulk of it and sand off what remains?

Once you remove as much of the glued layer you can rent a floor edger to grind off the rest. Use 16 grit edger discs. Another way is to buy an electric planer from Harbor freight, they have carbide blades. Be sure to buy the extended warrantee. Nail holes can be filled with wood patch if you are careful. If the residue is old glue that resists sanding, use paint remover and a putty knife. Start on one side and after the glue dissolves use a putty knife to move the residue across the floor a little at a time. Cover with plastic film overnight for best results

You can also set a skill saw to almost the depth of the plywood and cut crisscross on it. Small chunks are easier to get off than prying on the whole thing.

Thanks floormeintucson and Pete A. for your suggestions!