Reinstallation mac os x el capitan
I'm assuming you have a copy of the El Capitan DMG, see here if you don't. I also assume that your flash drive is empty - if it's not, back up any files before you start as this will wipe everything from the drive.


Insert your flash drive in to your computer and run Command Prompt as administrator.
Type diskpart and hit Enter.
Type list disk and hit Enter.
Locate your flash drive in the list and identify what number it is, then type select disk X (replace X with the number of your flash drive). Hit Enter to execute the command.
Type clean and hit Enter.
Type convert GPT and hit Enter.
Type create partition primary and hit Enter.


Your flash drive is now clean and has a GPT format ready for use with a macOS disk image. Now you need to download and install TransMac (and use the trial).

Once TransMac is installed, follow these instructions:


Run TransMac as administrator.
Right-click your USB drive in the left pane and click Restore with Disk Image. Click Yes on the dialog box that opens.
Browse for your El Capitan DMG file and then click OK to write the image.
Now, wait - this process could take a long time.


Once the disk image is written and TransMac has completed the process, eject the disk and plug it in to your Mac.

To run the installer on your Mac, plug it in and hold down the Option key while you turn it on. Click the disk when prompted and run through the installer.