Auron is right we're getting into changing actions as well as beliefs, but yes, you can change your beliefs on a whim as long as you have a desire to change it equal or greater than the benefits of maintaining the current belief. 

The reason people don't usually change their belief is they have something either pleasure inducing or pain relieving associated to that belief.  IE: The belief that a relationship is wonderful to have will lead to having a wonderful relationship - a pleasant experience (or so you believe).  Now if you just got out of a painful breakup that belief may change.  Now if you want to change it on a whim, then you can do so by convincing yourself that relationships just lead to painful breakups, prior to having one - this belief would be pain relieving then.  Why on earth you would want to is beyond me, but for arguments sake, yes, it's doable.

It that brain washing?  In a way, yes, but it's choosing what you want to believe.  Like it or not your surrounded by brain washing all day every day from advertisments, to peer pressure, to the War on Terror to Zeitgiest to religion to your parents teachings, it's all some form of 'brain washing' created to alter your beliefs.  Some are for your benefit (parents and religion generally teach positive ways to live) but most are for others benefits.

 That's not changing your beliefs, that changing actions based on a punishment/reward system. It's just a behavioral explanation. The belief system becomes a justification for the actions. You're giving an example and then proving the point by manufacturing an outcome that proves your point. It's not very convincing.

The question of free will is whether, and in what sense, rational agents exercise control over their actions and decisions. Addressing this question requires understanding the relationship between freedom and cause, and determining whether the laws of nature are causally deterministic. The various philosophical positions taken differ on whether all events are determined or not—determinism versus indeterminism—and also on whether freedom can coexist with determinism or not—compatibilism versus incompatibilism. So, for instance, hard determinists argue that the universe is deterministic, and that this makes free will impossible.

The principle of free will has religious, ethical, and scientific implications. For example, in the religious realm, free will may imply that an omnipotent divinity does not assert its power over individual will and choices. In ethics, it may imply that individuals can be held morally accountable for their actions. In the scientific realm, it may imply that the actions of the body, including the brain and the mind, are not wholly determined by physical causality. The question of free will has been a central issue since the beginning of philosophical thought.

- Wikipedia
Edit: sorry I forgot the link. http://en.wikipedia.org/wiki/Free_will - pretty interesting

Note: Actions are determind by the mind so what they are talking about here does apply.

I believe you do have free will, there may be consequences for those things, what you believe may be separate from reality, but in the end it is up to me the paths I create or follow. Some argue saying you always have a choice means you have no free will because your a merely choosing the set choices. On an extreme level you have x amount brain cells and y amount of things that can be done with them. This could be considered limiting free will. Do you have more free will then a cow? Then there’s talking about control of the mind. Does a schizophrenic have free will?

The fact that I can choice to believe any of these things true or false I think is prove of free will.

*finally noticed the thread is in the Nintendo discussion board* I change my first statement now seeing where this thread is, Nintendo tells you what to believe and thats the only thing to believe anything else is lies and fanboyism, and any mishaps in this logic can be blamed on Wii Fit.

OMG that clears up everything i have ever known

That is changing your beliefs.  In the given example you no longer believe that relationships are wonderful.  Which is a detrimental belief BTW. 

Every single belief you have your subconscious mind has adapted because it does (or did, people often maintain belief system long after they stop serving them) bring you into pleasure or avoids pain.  All I'm saying is - Yes it's possible to alter those beliefs consciously as well.  

Now someone will argue, that people believe they are powerless to (for example) get out of a abusive relationship and that belief isn't going towards pleasure or away from pain.  But it is - It avoids a greater fear of change.  Change is more painful mentally or emotionally than staying the in the abusive relationship.  This is a belief should be changed ASAP.

Fact is people do change their beliefs all the time, but normally because some outside occurance or information prompts them to do so by making the old belief less appealing than a new one.

Could anybody here choose to believe in Santa claus starting now? No. You could say you do, but any rational person would not be able to actually to suddenly believe that there is a fat white guy at the north pole with a band of elves making toys and delivering them across the world in one night. You can't MAKE yourself believe that.

You can try to adjust your world views, philosophies, you can try to live your life in a different way. But to simply make yourself believe something that you do not believe cannot be done, unless you go to some extreme lengths to brainwash yourself.

I agree 100%.  But for the younger members out there: Yes, there is a Santa Claus.

Alright for instance, I became an atheist. I didn't "decide" not to believe in god. Rather I studied religion, many religions. I believed in god to start with, I was raised to believe in god. But the more I studied the more I read, the more I moved to agnosticism. I just wasn't sure any more. Then I continued my studies, both secular and religious and looking at all the information on the table, my agnosticism gradually moved towards weak atheism. This went on until one day I realized I didn't believe in any deities at all, the thought of Yahweh, Vishnu, Zeus Allah, or any others was preposterous given what I knew.

Now then, could I right now this very instance change my mind and believe in God? No, I cannot. Reason prevents me from doing so. I cannot just say that I will pray to Jehovah and he will hear me, and one day save me. I could lower my head and think some thoughts and pretend I am praying, but that doesn't mean I legitimately think some mysterious invisible man is listening.

You can change your mind based on information you're given, but you can't deny what you know to be true, and change what you believe contrary to what you know.