Creating an Image Backup using Win32DiskImager
This page will detail how to backup your SD card to an image file.
Downloading the Win32DiskImager program
You will need to download and install the application (for free) from SourceForge:
Insert your SD card
Insert your SD card into your computer or if you have a Micro USB with SD card, you might want to use a USB thumbdrive instead.
Note: If you are copying a Raspberry Pi card, the size will show around 55MB NOT the full size of the memory card. This is because Windows can only see the first partion which is a FAT32 partition and the rest is hidden.
This is most likely the same tool you used to write the image... it however, can be used to read and save the image as well.
This will display a box like:
Using the 'folder icon' on that screen, locate a place where you want to save the image. You will need to remember this location and you will want to use a name that describes what the image is so that at a later date, you can identify exactly what the image contains and be able to restore it or use it to make additional copies of the image to memory cards.
This will now show the win32diskimager box to look like the following:
Click on the Read button to start the read process.
This will take some time... a 16GB image took approximately 30 minutes.
Unless there was some sort of read or write error, you now have a backup of your current image.
You can now copy this image to a new card, or if you corrupted your previous card, restore the image to the card and start from when you last made the backup.