Download Win32DiskImager from the Raspberry Pi Downloads Page or from http://sourceforge.net/projects/win32diskimager/files/latest/download
Insert your SD Card and then run Win32DiskImager.exe. It may give an error message on startup, but you can often ignore it. It should find your SD Card drive or if not select it. Select the file '#.img' image file you wish to use and then press write. Once it completes you are ready to go, insert your SD card into the Raspberry Pi.
Writing Your Own Custom SD Card Setup To A File
Ensure the Device drop down box has the drive your card is inserted into.
Press the folder button and select the folder and filename you want to use to write your image file to.
Press the Read button.
Example Instructions To Email To Someone
Here's the instructions to install your SD card ready for the Raspberry Pi.
1. Download and install Win32 Disk Imager from this link:
2. Download the following file to a computer with at least <<<#>>>GB of free disk space.
<<<<LINK TO YOUR FILE >>>>>
Unzip it (this may take a while as its a large file to match the size of the SD card)
3. Plug the SD card into a SD card slot or adaptor for your PC.
4. Run the unzipped Win32DiskImager.exe application (may just be shown as Win32DiskImager depending on your windows settings)
Ensure the correct driver letter is selected for the SD card – double check this is right in Windows Explorer as Win32DiskImager will overwrite the entire drive without warning if the wrong drive is selected!
Select the unzipped <<<<YOUR FILE NAME>>>.img file
Press Write and wait for the program to write the operating system onto the SD card.
5. Once the writing is done plug the SD card into the Raspberry Pi and power it up.