Even though the words "hypothesis" and "theory" are often used synonymously in common and informal usage, a scientific hypothesis is not the same as a scientific theory. A Hypothesis is never to be stated as a question, but always as a statement with an explanation following it. It is not to be a question because it states what he/she thinks or believes will occur.
According to the United States National Academy of Sciences,
Some scientific explanations are so well established that no new evidence is likely to alter them. The explanation becomes a scientific theory. In everyday language a theory means a hunch or speculation. Not so in science. In science, the word theory refers to a comprehensive explanation of an important feature of nature supported by facts gathered over time. Theories also allow scientists to make predictions about as yet unobserved phenomena, 
A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment. Such fact-supported theories are not "guesses" but reliable accounts of the real world. The theory of biological evolution is more than "just a theory." It is as factual an explanation of the universe as the atomic theory of matter or the germ theory of disease. Our understanding of gravity is still a work in progress. But the phenomenon of gravity, like evolution, is an accepted fact.
I'll let you follow the above links to learn more about the differences. In a nut shell, a hypothesis is a suggested explanation of something observable. A scientific theory, on the other hand, is an explanation for a phenomena. Basically, a theory, is the best explanation for why or how something observable occurs. The whole foundation for a particular scientific theory is a set of facts. For all intents and purposes, scientific theories are tentatively held as facts. I say tentatively (and extremely unlikely) because science, by it's nature and methods, is tentative. It changes when new data are presented.
Given all that above...theories are not there to be believed. The question, "do you believe in the theory of (insert theory)" is nonsensical. Either a theory works or it doesn't and is throw out. Here are some common theories. Do you disbelieve any of these?
Germ Theory of Disease: Basically, Louis Pasteur figured out that there were these tiny invisible organisms that cause diseases. Imagine that. It wasn't curses, god's wrath, bad energy or imbalanced humors that was killing people. In my opinion, Germ Theory is probably responsible for saving the most lives of any other theory. Go ahead and kiss goodbye hand washing and antibiotics without this theory.
The Theory of Gravity: Newton came up with a pretty good explanation for why and how an apple falls and why planets orbit the way they do. However, his explanation wasn't perfect, so people like Einstein came along and built upon Newton's work. Isn't science wonderful. When faced with better ideas, science adapts.
The Theory of Electromagnetism: You can thank James Clerk Maxwell for this one. Without this explanation for magnetic fields, we very likely wouldn't have electricity.
Atomic Theory: "In chemistry and physics, atomic theory is a theory of the nature of matter, which states that matter is composed of discrete units called atoms, as opposed to the obsolete notion that matter could be divided into any arbitrarily small quantity." Without these theories, you can kiss your periodic table and all the plastics, medicines and most of your food and clothing goodbye.
Cell Theory: These theories explains the relationship between cells and living things. You can kiss most of our modern medicine goodbye with out this explanation.
Systems Theory: I'm sure there is a lot of cool shit this collection of theories explains, but I'm way not smart enough to comprehend it: "it is a framework by which one can analyze and/or describe any group of objects that work in concert to produce some result. This could be a single organism, any organization or society, or any electro-mechanical or informational artifact. Systems theory first originated in biology in the 1920s out of the need to explain the interrelatedness of organisms in ecosystems. " It's used in everything from biology to engineering to computing and even psychology.
Mathematics is filled with theories. Without them, we wouldn't have all the numbers and stuff we have around today. Just try to design, build or model something without math. I dare you.
Go here for a not so exhaustive list of fields of study, each of which contain lots and lots of theories. I've relied heavily on Wikipedia for this post. Don't take my word for it or even Wikipedia's word for it. Do your own research and think critically about everything.