The sounds like moisture condensing from big air leaks around the house perimeter. An insualtion expert could do a better job, but check in the basement or crawl space for lack on insulation around the perimeter, and correct it.
I have black stain along the baseboard all over my house. How or what can I use to take it out.
The post is vague. Try adding details so we know what you're talking about.
Are you removing the baseboards? Is this black material growing on the baseboard? Are the baseboards been stained black and you want to change to a different color?