If you have a solid hardwood floor, chances are at one point you'll need to sand and refinish it. For this arduous task, you'll need at least three pieces of expensive equipment: the drum sander, vibrating sander, and edge sander.
Luckily enough, these sanders are easily found at your local tool rental yard. Just search the internet for "tool rental [your city]".
This is the real workhorse of hardwood floor sanding. It's a massive piece of equipment, too heavy for most people to lift. Two people are required, and even then they should be very strong people.
The drum sander consists of the sander itself, a large dust bag, and a drum on which you attach large sheets of sanding paper. Be absolutely sure to buy the sanding paper at the tool rental yard, and you probably won't find it at your local Home Depot or Lowe's and certainly won't find it at a local hardware store. The rental yard employees will recommend at least three gradations of coarse, medium, and fine sanding paper. Be sure to overbuy sanding paper, as most rental yards will buy back unused paper (but confirm this first with them).
The drum sander rips off the bad spots, the high spots, stains, paint splotches--you name it--from your floor. It truly will take the floor down to bare wood. Unfortunately, if you're not careful, you can carve unsightly, permanent grooves in the wood. It's easy to strip off a quarter inch of wood without even noticing it.
After using the drum sander, the next step is to smooth out the wood with a vibrating sander.
Roughly the same size as the drum sander and also employing a dust bag, the vibrating sander will come as a welcome relief from the drum sander. It's lighter, there's less danger of hurting the wood, and because of the vibrating motion, it's easier to move across the floor.
Another option is to use a large orbital sander also available at the tool rental yard.
Either the vibrating or the orbital sander will take your hardwood down to its smoothest finish.
As the name implies, the edge sander gets in those hard-to-reach areas that the drum sander and vibrating or large orbital sander can't reach.
Unlike the drum or vibrating sander, the edge sander is hand-held. It does have a dust bag, though, and does have an orbital motion.
The edge sander is not the Black & Decker you might have in your garage. It's heavy, expensive, and has the kind of power you need to sand down hardwood floor. Please don't think of using your own orbital sander, as this will only lead to frustration. The edge sander is relatively inexpensive to rent and will make your work go faster.