A newly unpacked MBPr shall run W7. I have partitioned the SSD 50/50 with disk utility. One OSX partition, one MS-DOS FAT32. When I reboot and select the USB stick to install, I get a black screen with a message on top "...failed to load BOOTMGR". This happens trying both USB ports and with any type of USB stick.
Reason why I partitioned with disk utility was that Boot Camp-Assistant did not give me an option to install from the USB after it downloaded drivers to that USB.
Any hints much appreciated!