Check the frame rates throughout your project. I bet that's the problem.
What do you mean that it's in slow motion? Are you sure that the problem isn't that you created a file so large that your video player and computer can't play it in real time?
See this page:
I'm not trying to be rude but you didn't give us anything to go on except to guess that you rendered an uncompressed versioin of your project. If that is not the problem then we need to know the frame rate of your composition and exactly how you rendered the composition including whether or not you used the Render Cue or the Adobe Media Encoder, what the setting were, and what kind of a machine you are using.
What the otehrs said: Read up on that stuff! Not just the AE help, but on CoDecs, file formats and al lthat in general.