I need held with my Nikon d5100?

I have a nikon d5100 and i just got it so i'm not really that sure what i'm doing. I wanted to know why everytime i take videos it last 5min or less now last 10 but what if i need to take hours of video? Help me. If you have any websites for beginners that would be so helpful.
P.s. Can some one explain what the ISO or how how i can't set my pictures for bright days or dark days?

You have unrealistic expectations.

dSLR's with CMOS sensors just get too hot to do what you want

You really need a proper video camera, NOT a still camera with a video feature.

Most of us who shoot video, shoot from a script which has been broken down into a shooting script. Takes on each scene rarely last more that three minutes

Take a look at your script and see how long each take is. Shooting video is really not a "stream of conciseness" process.

ISO? That is the sensitivity of the sensor to light. In bright sun, usuall 200 is used. In deep dark, dimly lit sets, would 3200 ISO is used. But that does not tell you what you really need to know. When shooting in what would be considered "low light", the lighting director brings in lights to bring the overall lighting up to a lux that will allow shooting at lower ISO's like 400 or 800. The additional lighting emulates the lighting as it was, but just adds more of it.

Natalie, how much time have you spent actually reading & studying the Owner's Manual for your new camera?

This video will also help you: http://www.nikondigitutor.com/eng/d5100/index.html Who better than Nikon to teach you to use your Nikon D5100?

Between the information in your Owner's Manual and the Nikon video you will learn what ISO is, what Aperture (aka f-stop) is and what Shutter Speed is. Those 3 terms make up what's known as the Exposure Triangle. This site will also help you understand the Exposure Triangle:

http://www.digital-photography-school.com/learning-exposure-in-digital-photography This site has numerous tutorials suitable for the beginner so you might want to explore the site further.

About 95% of my photography is done with ISO 100 and my camera in Aperture Priority. I learned to shoot in Manual 40 years ago - when it was the only option.

Enjoy the photography learning experience. It never ends.