Yes,It is possible.in fact I am doing it right now.Windows 7 and Windows 8 can be installed onto a GPT drive as they support it except for Windows XP.Though they wont create the EFI partition (Sytem Reserved 200 MB partition That you'd see).
Follow these steps:
1.You have to shrink your Mac Partition and make space for Windows if there ain't any,Format it as NTFS or FAT 32 otherwise Windows installation won't recognise it.
2.Then boot your Windows installer by USB or DVD whatever you wish.
3.Then install Windows on that Windows partition that you created.
// Now Windows will take over the boot priority thus you wont be able to boot from the mac bootloader.
4.So stick in your USB Mountain installer and use that bootloader to boot into your mac.
5.Then reinstall your preferred bootloader on your main hackintosh partition(root) and you will be set.
Now if you restart you will see your windows partition in your bootloader( but no system reserved partition).Select whichever OS you''d like to boot into.