In windows 10 preview you can write the iso to the drive using terminal. It will be bootable, You should be able to find your partition with terminal to write to a specific partition.
http://askubuntu.com/questions/59551/how-to-burn-a-windows-iso-to-a-usb-device
"
Insert the USB device and then open Disk Utility (in 10.10 and older, System -> Administration -> Disk Utility).
Select the USB device from the list in the left of the program and detect where it was mounted: /dev/sd[1 letter][optionally 1 number]. For example, /dev/sdc or /dev/sdc1.
Make sure the USB device is unmounted (not safely removed, but unmounted) If it is mounted you can unmount it:
sudo umount /dev/sd[1 letter][optionally 1 number]
Assuming the .iso file is in your home folder, open the terminal and write:
sudo dd bs=4M if=[ur .iso] of=/dev/sd[that 1 letter]
Example:
sudo dd bs=4M if=windows7.iso of=/dev/sdc
"