Download Win32DiskImager and grab the latest Raspbian Wheezy Linux distro. Unzip both files to appropriate folders grab a 2GB or larger SD card plug it into your PC and fire up Win32DiskImager’s .EXE file.
Select the .IMG file from the unzipped Raspbian download choose the drive letter for your SD card and click ‘Write’. Once it’s complete you can plug the card into your Raspberry Pi boot up and follow the prompts. (The initial boot will expand the distro to use all of your card’s storage space.)