Today I am gonna help you to recover your data after your Windows Operating system fails to boot means doesn't startup.
The basic of this is procedure is to LIVE BOOT a Linux OS and get access to your Windows Partition and then copy your data to any external hard drive or pen drive.
There are many Linux Distros available free of cost which you can download and use. For LIVE booting also there are many tutorials available which you can search if you want more on LIVE BOOTING. I am here just will concentrate on fastly getting the data back with the simple and direct steps available and will LIVE BOOT using USB.