Linda, "Hi" The only thing I can maybe help you with is first " DONT USE THE POWER SAW" if you do not have the skill, or you may be going to the hospital in parts you and your fingers in a plastic bag. OK, first make sure there are no cable/elctric wires, pipes under the partical board, then drill some holes along one side of the wall/panel this is so you can get a wood saw through the floor ( take care not to damage the side panel )you can buy a new saw "cheap" partical board is made up of all kinds of things, so dont buy a good one just a sharp one, and just cut along the edge on both sides. To replace the old partical board ( I like that word ) we call it chipboard you will see what I mean when you saw it. you will have to buy a panel of plywood 3/4"(18mm) if you ask at the store what it is for, they should give you waterproof plywood. Now this is the hard part to explain. From the top surface of the old partical board, mesure down to the ground/floorboards, let us call this mesurement "X" take off the thickness of the new plywood you will have a size "Y" then run two timbers the size of "Y" along each side ( left and right side ) place the plywood on top and fix it Now you have a new flooor. If that don't work get the guy from next door to do it. Good luck. John 2000.