I just did part of a hallway by hand. Well, with a hand belt sander and an orbital sander. It sure was slow going but I just wanted to get down through the old finish and that was it. The old varnish and wood are very hard.
What condition are the floors in now? If not bad you may be able to get away with using screens on an orbital to refinish.
If you need a more aggresive approach then look for a floor Belt Sander as opposed to a drum sander. The belt sander will be easier to control and produce less chatter. Here's a nice how-to article:
http://www.canadianhomeworkshop.com/diy/refinish_floors.shtml