OK. I am thinking of downloading the demo of Unity. If was to make a game, would I be able to put it on a disc and play it on another computer without installing Unity? In other words, to do you have to play your game in Unity? Thanx for your help.
Nope, you choose File->Build and save your built game that is entirely self contained.
-Jon
Soooooo, pretty much, I can burn the game to a CD, pop it in another computer (Without Unity Installed), and the game will pop up for me to start playing? Also, is there a way to make a menu so that you can choose to start playing without the game just starting right away?
Sorry for the newbie questions.
You can make a menu.
By default unity pops up a resolution / control configuration dialog. Then it launches the first scene. If you want to make a game menu (start new, load profile, whatever) you can do that.
To Unity, a menu is not a special thing; just a simple scene with a camera filming some text objects. Then you make some simple scripts to handle what actually should happen (e.g. clicking on “Start New Game” will load the first level).
To clarify: the game won’t start playing when the CD is inserted. The computer will show the contents of the CD, which will include the game you wrote. The user can then run the game if they want (or copy it to their hard drive.)
It is possible to have a CD auto-launch, at least under OS 9 and Windows. (Not sure about OS X.) That’s usually called “autoplay” and it has nothing to do with Unity. In Windows for example, Windows looks for a file with a certain name in the root directory of the CD. That file tells Windows what to run off the CD.
So if you want to have something run off a CD automatically then you have to build the CD a certain way. Doesn’t matter whether you use Unity or not.
And as others have already said, Unity lets you build stand-alone applications that can be run on computers that do not have Unity installed.
Also autoplay is disabled on most computers (It has never been possible on Mac OS X and I think it is disabled by default on Windows XP) – this is due to security reasons, I reckon.
To further clarify: by “computer”, that means “Mac” specifically. The demo doesn’t produce stand-alone games that run on Windows…you need Pro for that.
–Eric
To clarify the clarified clarification: if you want to test on a Windows machine, and it doesn’t have Internet, just publish a Web player and copy the Web player to a CD. It’s not very polished to have a CD game open into a browser (and there’s the little Indie watermark), and Web players lack the input-customization window, but a Web player can still go to full-screen (right-click for this) and is suitable for basic demonstration and testing.
To further clarify the clarification of the clarified clarification: but you’d need to download the Unity web player if the machine didn’t have it installed, so without Internet access that wouldn’t do much good. And if you have a Mac, you’re not going to have the Windows web player, so you can’t just copy that onto the same CD.
But anyway, yeah, you can publish a web version to use on Windows machines…who doesn’t have Internet access these days? Takes a bit to download the player on dial-up though.
With all this clarity, I can see for miles now. 
–Eric
if you go to Unity Real-Time Development Platform | 3D, 2D, VR & AR Engine you can download the web-player installer for other platforms as well.
All this clarification is quite confusing. If the clarification get’s clarified one more time it will be completely incomprehensible. 
-Jeremy
To clarify this, if you do make a built version for Windows with Unity Pro, then it won’t have an input customisation window anyway. When 1.6 is released, it will.
Thanks for the clarification 