My brother got a "deal of the day" on 3/4" oak flooring (my carpet is shot). My kitchen can use a tile floor (linoleum is worn) as long as we are at this. This home was built in 1974. I took up the carpet/linoleum doorway to find a base of 1/2" plywood. The kitchen has 3/4" particle board that is screwed down under 2 layers of linoleum (Does it matter if I wreck the plywood underneath if I pry-bar it?!). The living/dining/hall has 1/2" particle board nailed down (much easier!). Four stores later...I have four opinions on what I need to do next. My best guess (after reading several postings here) is to rip up all particle board, use "hardibacker" in the kitchen for the tile, and a second layer of plywood (thickness...1/2 or 3/4"?!?) in the living/dining/hall for nailing the hardwood. I still don't know the best way to avoid squeaks between floor layers, and if the height difference will be OK in the doorways to the kitchen (tile with 1/2" "hardibacker" would still be 1/2" off if the new plywood should be 3/4")! OH...I was told the cabinets should be taken out...or there is a saw that will cut right up to their edge. Love some ideas!