Windows 7 Recovery Disk: Operating System Isn't Found

I’m sorry you’re dealing with this, MUHD SHAHRUL NIZAM BIN ZAINUDIN.

That said, before getting further, I need to note that Windows 7 reached end of support years ago. Because of that, we cannot reproduce or verify the recovery procedure on the same environment. I will try my best to give suggestions, but it may not be identical to your exact system/interface.

Now, since the issue seemingly appears after you deleted some a registry key, the top solution would be to check whether there's a registry backup and restore it. Let's start over and enter Command Prompt window, and run the commands below one by one:

• Back up the currently installed registry hives first with:
  • cd /d C:\Windows\System32\config
  • mkdir DamagedRegistry
  • copy SYSTEM DamagedRegistry\
  • copy SOFTWARE DamagedRegistry\
  • copy SAM DamagedRegistry\
  • copy SECURITY DamagedRegistry\
  • copy DEFAULT DamagedRegistry\
• Check the registry backup with dir RegBack > check the key mentioned above
• Confirm they are present, size bigger than 0, and dated before the deletion.
• If those conditions are met, restore them:
  • copy /y RegBack\SYSTEM SYSTEM
  • copy /y RegBack\SOFTWARE SOFTWARE
  • copy /y RegBack\SAM SAM
  • copy /y RegBack\SECURITY SECURITY
  • copy /y RegBack\DEFAULT DEFAULT
  • exit
• If the files are copied successfully, remove the USB drive and restart.

If the RegBack files are missing, empty, or cannot be copied, the deleted registry information cannot be reconstructed reliably. For future, please make sure: How to back up and restore the registry in Windows - Microsoft Support. The remaining option is to back up your files from C: and perform a clean installation, preferably using a currently supported version of Windows. Let me know and I can give instructions on saving as much data as possible.