The black padding you are reffering to most likely was from rubber back carpet that was glued to your floor. Depending on what new product you are putting in as to the degree you have to remove it. their are tools to help you (scrapers& stripper machines ) if the job is large enough. If recarpeting and you got the black backing up but have left a small black film on your floor, you may carpet right over that with new cushion. Let me know more information on what your planning and I will be happy to guide you.