I installed the Vista Bootloader, installed EasyBCD, repaired the Bootloader and tried to add OSx86 to the Boot-List. There were a MBR and a GUID/EFI option, but no GUID/Emulated-EFI option. EasyBCD said, I need a .efi-file from i386, but this file doesn't exist in my system. And the chain/chain0 mode doesn't work as I know already, because it's only for MBR. After Googling I experienced, that there's no way to add a GUID HDD to the Vista-MBR bootloader without OSx86-Vanilla.

Means: I have to change the Boot priority on every boot, when I want to start Windows (in german we say: Win<i>doof</i> - "doof" means "stupid"), but that's not very often.

Thanks guys for your help anyway,
-crawle