Dear Denise
You remove an old floor the opposite way it went in. Start at the far end of the room where the last few boards were laid. These will have their tongues pointing toward the wall. The last 2-3 rows will be face nailed. You will only have to crack one board in the last row to remove it. Then use a cat's paw restorer at http://www.leevalley.com/wood/page.asp?SID=&ccurrency=1&page=32014&category=1,43456,43399.
This tool will gently remove the boards without damaging them. Try to scoot the thin edge of the catspaw under where the floor is nailed, and pry just a little at a time. Once you work backwards into the room and get some working space you can use a larger tool: http://www.leevalley.com/wood/page.asp?SID=&ccurrency=1&page=32015&category=1,43456,43399. The renovator bar will ease up the most stubborn boards.
I know you will want to use a hammer and screw driver for this instead. But it is a pleasure to work with good tools and you will be saving valuable wood in the process.
Oh, and once you have the board removed half the nails will still be in the boards, these you can remove by gripping the nail just where it comes out the Back of the board, with a nail puller: http://www.leevalley.com/hardware/page.asp?SID=&ccurrency=1&page=32024&category=3,41306,41331
Pull the nail through the BACK of the board. This works better than hammering it back the way it came in because even though it will make a hole in the tongue, it won't damage the face of the board.
While you're at Lee Valley there is one more tool called a nail spinner which is invaluable for installing the last few rows where the power nailer cannot reach: http://www.leevalley.com/wood/page.asp?SID=&ccurrency=1&page=32273&category=1,180,42334
Oh, and as to your other question of how to install this wood to a concrete subfloor, we have an article on this very subject, which can be found at the top of the web page in the search box. This article details the 3-4 different methods of fastening this type of floor to concrete. It will be a difficult job in any case, but there is enough info in the article to help you through it, if you have some carpentry experience.
