How to remove write protection from SD card?

Hello,
I have got problem with SD card while downloading a large file of 500MB from unknown source. So it hanged and I directly turned off my mobile and then turned ON. but then I found this error "Preparing SD card" "Checking for errors" And I could not access my SD card. I also checked my card on some other mobile, data was available, but it was not giving access to data. I have tried all types of formating my SD card it, but in vain. I don't how to do it. Can anyone help please?

I have already following methods:
1. Regedit: HKey_Local_Machine, found Storage Devices, create WriteProtection key and insert value 0........... Not working.

2. Go to My computer.......Manage---->Disk management---->Select disk--->format.................Not working.

3. Go to start menu, open command prompt...... write 'Diskpart'..... write " list disk "............... write " select disk ".............. Attributes disk clear readonly............ Invalid argument or format, not working........

4. I downloaded SD card formatter software, but it says SD card is write protected.... This also didn't work.

Any different method please??