Hi zwerg, more details would be helpful. Have you tried using BootCamp? If so, have you gotten any specific errors, and when did you get them (e.g. durring the partition phase or when tying to install windows, etc.)? Thanks.
All Macs use the GUID partition table. If you're trying to install Windows with EFI install, you should know that you can only do this with Windows 8 and Apple doesn't support this kind of installation, so it can fail and damage the Mac. The best way is to use Apple Boot Camp