How to Boot Windows 7 off a USB drive on a Mac Mini with EFI / UEFI

G'Day,

I have a Apple Mac mini "Core i5" 2.5 (Late 2012) at home and the HDMI output isn't working as expected when plugging it into my Sony DVD sound system. So i want to see how Windows 7 handles it, but i don't want to dual boot as that might break my Mac OS. Bugger that.

So lets boot off a USB hard drive right? When the Mac boots up, just after it makes the chime sound Hold Alt key and it will allow you to boot from external drives.

I tried the approach in this link but it didnt work... said something like "system disk not found press anykey to reboot"
http://bleeptobleep.blogspot.fr/2013/02/mac-install-windows-7-or-8-on-external.html

That guy is using MBR for the boot record, and i read Macs use EFI or some malarkey. So i went looking at stuff. Here is what i dun so far.  :..:

To find out which Mac you have  you have get the serial number then plug it into here
https://selfsolve.apple.com/agreementWarrantyDynamic.do

Or you can put in your model number here and take a guess. You want to check if you have an Intel processor which i pretty much guarantee you do.
http://www.everymac.com/ultimate-mac-lookup/?search_keywords=A1347

So then if you believe what they say here, Intel-based Macs support starting from an external USB storage device's volume that has been formatted with a GUID partition type
https://support.apple.com/en-us/HT201663

I'm not sure what EFI and UEFI are all about but i saw this App. The screenshots seem to say that this app installs Windows and is expecting a GUID (GPT) EFI boot partition. Groovy. So i decided to go for it see what happens.
http://lifehacker.com/how-to-run-a-portable-version-of-windows-from-a-usb-dri-1565509124

To get my USB ready, I used diskpart from my windows laptop. I wanted it in the same state as the screenshot in the link above, which is a GPT EFI fat32 boot partition and a Primary NTFS partition for windows.

The only tricky part was that one of the first things you do is convert the disk to gpt. Which creates a reserved partition at 1. So I had this

DISKPART> list partition

  Partition ###  Type              Size     Offset
  -------------  ----------------  -------  -------
  Partition 1    Reserved           128 MB    17 KB
  Partition 2    System             350 MB   129 MB
  Partition 3    Primary            114 GB   479 MB


Which didn't match the picture. So i splatted that and started again. To match what they gave ...

diskpart
select disk 1
clean
convert gpt
select partition 1
delete partition override
create partition efi size=250
format fs=fat32 quick
create partition primary
format fs=ntfs quick
exit

Then i ran the app and installed Windows 7 as per the guide. Super sweet. I will test it out tonight - wish me luck.

Next time

Might need to assign drives letters?

Try this way?
http://www.sevenforums.com/tutorials/186875-uefi-unified-extensible-firmware-interface-install-windows-7-a.html

UPDATE:
well... it dint work, not the bloody mac wont boot. the apple log comes up, get half way down the load screen, stops then powers off.

So may as well try it again and see if i can get it going