How to take pictures of snowy areas?

I recently got a Nikon D3000, and when I try to take a picture of my backyard, which has a lot of snow in it, the picture turned out looking like a white screen, like you couldn't see the trees, or animals, nothing but a white screen.
I had it set on manual without the flash, and then I put the flash up to see if it would change anything but it didn't. What setting should I put it on and how should I shoot it?

AF (Automatic and put it on the flower dial)

There are lots of hints and tips on the net:

http://www.photoradar.com/techniques/technique/how-to-photograph-winter
http://www.digital-photography-school.com/?s=winter
http://www.dpmag.com/search.html?q=winter

Snow and water can have a lot of reflection in direct sunlight which would burn the high lights. Use the manual setting and close the aperture a bit to get the right exposure. To start with try, f-16 at 1/125 seconds.

What setting did you use on manual? Obviously the picture was over-exposed if all you got was white. Did you follow the sunny16 rule, meter the scene first, or just guess?

My advice, put the camera on program mode, set the ISO to 100 or 200, and take another snap. If the snow looks grey (and it very well may) dial in +1 exposure compensation.

The next step is to take a class or visit the library for a book on basic photography so you can learn how to form your exposure using shutter speed, aperture and ISO. Much easier and a better way to learn the craft than simply changing the settings willy-nilly without knowing why. Have fun with your new camera!

It's clear that you don't understand the correct use of manual mode. So why are you using it? You basically overexposed the scene so far that nothing was even near a proper exposure. Adding a flash would just make it worse. Try increasing the shutter speed, stopping down the aperture, and reducing the ISO. Better still, put it on P mode or full automatic. Take the shot. Observe that snow will appear gray. Note the shutter speed, ISO, and aperture that the camera selected. Switch back to manual. Dial in the settings that you noted. Reduce the shutter speed and/or open up the aperture the equivalent of one to two F-stops. Shoot. Voila.

If you are using manual mode because somebody told you that real photographers always shoot manual, that person is either an idiot or a poser.

If you put the flash up, then you still need to change shutter speed, aperature, and ISO.
Heres a chart that might help http://www.dgrin.com/showthread.php?t=30235

Use Aperture Priority and +1 or +2 EV (Exposure Compensation) for your snow pictures. You can check the results and decide which overexposure setting gives the results you like. If you don't set your camera for the overexposure the snow will turn out a dingy gray.

You can also meter on a dark area in the scene, lock the exposure and then compose and shoot.

In Manual Mode you must first set the aperture and shutter speed based on the meter reading and then open up 1 or 2 stops. This is how we did it back before there were cameras with Aperture or Shutter Priority settings. Or we'd meter a dark area and set that exposure then compose and shoot.

Camera in Aperture Priority with +2 EV and a circular polarizer.

If you know how to use the manual on your camera you need to underexpose.