Here You Go:

From Windows, open a “Command Prompt with administrative permissions” window. Type the diskpart command and press return. Type the list disk command and press return to view a listing of drives connected to your computer. Type the select disk command followed the number assigned for the USB flash drive (e.g., select disk 4), and press return. Type the clean command and press return. Type the convert GPT command and press return. Type the create partition primary command and press return to complete the task.

Install Transmac trial.

Insert the USB drive that you’ll use to fix your installation of OS X. Remember that all the data in the USB will be erased. Make sure you take off any important documents.

Right-click the TransMac software icon and “Run as administrator”. You’ll be prompted to “Enter Key” or “Run”, because we’ll be using it once, click “Run”.

On the left pane, you’ll see all the Windows PC drives listed. Right-click the USB drive you’re intending to use to reinstall Apple’s OS X and click “Restore with Disk Image”. Use the “Restore Disk Image to Drive” dialog box to browse for the DMG file with the installation files (for Mac OS X Yosemite in this case), and click OK to create a bootable USB of the Operating System. Now wait. Go have a snack. Do your anterior pelvic shift exercises. May take 1-2 hours.

Once your bootable USB installation media is ready, remove it and insert it into your Mac, power it on, holding down the Option key, and select the USB you just created to reinstall Mac OS X.

If you’re having issues trying to create a bootable media, you can get a USB flash drive that comes with Mac OSX ready to install.

Here You Go:

While Windows is installed on the OP's Mac, this answer assumes the Windows machine is not a Mac.

From Windows, open a “Command Prompt with administrative permissions” window. Type the diskpart command and press Enter. Type the list disk command and press Enter to view a listing of drives connected to your computer. Type the select disk command followed the number assigned for the USB flash drive (e.g., select disk 4), and press Enter. Type the clean command and press Enter. Type the convert GPT command and press Enter. Type the create partition primary command and press Enter to complete the task.

Install Transmac trial.

Insert the USB drive that you’ll use to fix your installation of OS X. Remember that all the data in the USB will be erased. Make sure you take off any important documents.

Right-click the TransMac software icon and “Run as administrator”. You’ll be prompted to “Enter Key” or “Run”, because we’ll be using it once, click “Run”.

On the left pane, you’ll see all the Windows PC drives listed. Right-click the USB drive you’re intending to use to reinstall Apple’s OS X and click “Restore with Disk Image”. Use the “Restore Disk Image to Drive” dialog box to browse for the DMG file with the installation files (for Mac OS X Yosemite in this case), and click OK to create a bootable USB of the Operating System. Now wait. Go have a snack. Do your anterior pelvic shift exercises. May take 1-2 hours.

Once your bootable USB installation media is ready, remove it and insert it into your Mac, power it on, holding down the Option key, and select the USB you just created to reinstall Mac OS X.

If you’re having issues trying to create a bootable media, you can get a USB flash drive that comes with Mac OSX ready to install.

Here You Go:

Open Command Prompt with administrative permissions. Type the diskpart command and press Enter. Type the list disk command to view a listing of drives connected to your computer and press Enter. Type the select disk command followed the number assigned for the USB flash drive (e.g., select disk 4), and press Enter. Type the clean command and press Enter. Type the convert GPT command and press Enter. Type the create partition primary command and press Enter to complete the task.

Install Transmac trial

Insert the USB drive that you’ll use to fix your installation of OS X. Remember that all the data in the USB will be erased. Make sure you take off any important documents.

Right-click the TransMac software icon and Run as administrator. You’ll be prompted to Enter Key or Run, because we’ll be using it once, click Run.

On the left pane, you’ll see all the Windows PC drives listed, right-click the USB drive you’re intending to use to reinstall Apple’s OS X and click Restore with Disk Image. Use the Restore Disk Image to Drive dialog box to browse for the DMG file with the installation files for Mac OS X Yosemite in this case, and click OK to create a bootable USB of the Operating System. Now wait. Go have a snack. Do your anterior pelvic shift exercises. May take 1-2 hours.

Once your bootable USB installation media is ready, remove it and insert it into your Mac, power it on, holding down the Option key, and select the USB you just created to reinstall Mac OS X.

If you’re having issues trying to create a bootable media, you can get a USB flash drive that comes with Mac OSX ready to install.

Here You Go:

From Windows, open a “Command Prompt with administrative permissions” window. Type the diskpart command and press return. Type the list disk command and press return to view a listing of drives connected to your computer. Type the select disk command followed the number assigned for the USB flash drive (e.g., select disk 4), and press return. Type the clean command and press return. Type the convert GPT command and press return. Type the create partition primary command and press return to complete the task.

Install Transmac trial.

Insert the USB drive that you’ll use to fix your installation of OS X. Remember that all the data in the USB will be erased. Make sure you take off any important documents.

Right-click the TransMac software icon and “Run as administrator”. You’ll be prompted to “Enter Key” or “Run”, because we’ll be using it once, click “Run”.

On the left pane, you’ll see all the Windows PC drives listed. Right-click the USB drive you’re intending to use to reinstall Apple’s OS X and click “Restore with Disk Image”. Use the “Restore Disk Image to Drive” dialog box to browse for the DMG file with the installation files (for Mac OS X Yosemite in this case), and click OK to create a bootable USB of the Operating System. Now wait. Go have a snack. Do your anterior pelvic shift exercises. May take 1-2 hours.

Once your bootable USB installation media is ready, remove it and insert it into your Mac, power it on, holding down the Option key, and select the USB you just created to reinstall Mac OS X.

If you’re having issues trying to create a bootable media, you can get a USB flash drive that comes with Mac OSX ready to install.