Here is what you need to do:
- Boot with a a bootable installer for OS X.
- Launch Disk Utility.
- Choose to partition hard drive.
- click on Options… button and select GUID Partition Table to overwrte existing GUID created by Windows 7 / 8.
- Quit Disk Utility and continue your OS X installation.
You may follow the instruction in Create a bootable installer for OS X Mavericks or Yosemite on Apple to create a bootable installer for OS X.
- Apple: Create a bootable installer for OS X Mavericks or Yosemite
- Apple: OS X
- Wiki: Disk Utility
- Wiki: Globally unique identifier