How to edit Yosemite Bootloader, startup manager

I got it sorted, it was probably my fault not understanding the options properly. The actual install can only be started by that last option that says eider:

remove windows 7 or later version

OR

install windows 7 or later version

So if you already have a Windows partition created you will see remove windows 7 or later version, you need to remove it and then it will change into install windows 7 or later version, after creating the partition again, it will restart and the install will begin.

If you already have the bootable stick previously created by these steps, just plug it without checking first two boxes (create boot stick, download support software), creating that stick would take hours.

I think Apple could make it more clear (the re-install part).

I attach answer here as you guys suggested.

SOLVED - Bootcamp Windows 7 installation without USB, ODD

OK, I'll explain how I worked it. I followed almost of all of David's method here and here, but there are little differences.

Before we start, please note that I'm using MacPro4,1 which does not support USB installation of boot camp and I detached ODD. Instead, I attached another HDD in Bay 2.

1. You need rEFInd, VirtualBox, NTFS support for OS X (like Paragon or NTFS-3G), a bootable Windows installation ISO. Service Pack applied ISO is also ok.
2. Update Mac firmware as recent one as possible. here
3. Open Boot Camp Assistant and download driver files into any usb. (Just 2nd option of 3 of boot camp. if your boot camp assistant does not have 3 options, it would be 1st option)
4. install NTFS support for OS X, rEFInd and VirtualBox.
5. Format a partition with MS-DOS(FAT) which is going to install Windows.
   • I recommend you not to use Boot Camp Assistant app to format. Use Disk Utility instead.
6. In terminal, type diskutil list and remember disk and partition number of target partition. In this example, I use disk 1 and partition 1. So, disk1s1

7. Unmount partition and set permission.

   diskutil unmount /dev/disk1s1
   
   sudo chmod 777 /dev/disk1s1
   

8. Create VirtualBox image with raw disk access. anywhere except bootcamp partition

   sudo vboxmanage internalcommands createrawvmdk -filename bootcamp.vmdk -rawdisk /dev/disk1 -partitions 1
   
   sudo chown $USER bootcamp*.vmdk
   

9. Open VirtualBox and create a VM. Just set disk as what you already made, and ISO file of windows installation.
10. Start VM and install as normally, BUT when you get in 'setting computer name' phase, shutdown VM forcibly.

11. Turn off VirtualBox, and delete all files in the boot camp partition (including BOOT folder and bootmgr file - If you can not find them in Finder, use terminal to delete them or change Finder option with defaults write com.apple.Finder AppleShowAllFiles YES)

    Of course, Before open finder, mount partition first. (If you didn't installed NTFS support, you can't mount or delete file)

    diskutil mount /dev/disk1s1
    

12. double click windows ISO and copy all of the item into boot camp partition
13. Reboot Mac and in rEFInd bootloader, select 'Windows NTFS volume'
14. Install windows again, but DO NOT format boot camp partition.
15. Installation is finished. When you see desktop, install Boot Camp Driver which you downloaded at Step 3
16. After boot camp driver is installed & if you can see 'Windows' on OS X boot loader (which you can enter by pressing alt/option), you don't need rEFInd anymore. You can delete it in OS X.
17. You will see bootup selection between 'Windows 7' and 'Windows Setup' when booting Windows. If you don't want to see it, Go to Control Panel - System - Advanced Settings - Advanced tab - Click Setting button which lies on 'Startup and Restore' section - Uncheck first one.