CREATING AN IMAGE OF AN OPERATING SYSTEM ON AN SD CARD
Unless you bought an SD card that was preloaded with a suitable Pi OS, you'll need to create an image of the OS on an empty SD card. The images for various flavours can be downloaded from www.raspberrypi.org and you need to write one of these to your SD card. Simply using Windows to copy the file will not work: you need to use a disk image writer like Win32DiskImager - it's free to download and use.
From your PC, go to www.raspberrypi.org and download your preferred operating system image in compressed (.ZIP) format. Save it to a local disk. Make a note of the default username and password from the webpage.
You should expect the compressed file to be a little more than 1GB and the uncompressed version to be 3-3.5GB, so ensure there's plenty of free space available before you start.
I have encountered problems with Win32DiskImager if you put the image on a network share and try to copy the image from there to your SD card. I don't think it's speed-related because my network is gigabit and even though the typical throughput from my server is 45MB/s, the program generates an error. It could be either because the filepath is fairly long - a short path certainly works - so put the image file in the root folder of your disk or share.
Open the ZIP file and extract the image file on to a local disk.
Download and install a copy of Win32DiskImager from Sourceforge.
Insert your SD card into a built-in or USB reader and identify its drive reference. If you're using a used SD card, check for any files of importance and remove them because the next step will over-write all the SD card's contents.
Start Win32DiskImager and choose the disk image to use and the drive to write it to. Clickto start the write process. When the process has finished, remove the SD card and insert it into your Pi.
For further information about setting up your SD card and for alternative means of doing so, please visit elinux.org.
The next section explains the steps you need to go through when you first boot your Pi with a new disk image.