I don't understand you. Do you mean Blockchain.info or the Blockchain of your Bitcoin-Qt? You can recover your private key / funds on Blockchain.info with your identifier, password or seed.
It is on blockchain.info. I stored it with a folder containing multiple documents in drive D. And after installing win it was lost.
How to recover my private key ? Plz help me
Do you mean private key in which you can import from? Or the indetifier that it uses on login?
And what someone else said be very careful with online, also keep track of keys.