Hide Boot partition without damage to it

I have specific question on which a cant find solution in Google for several days

I got Portable External Hard Drive 2.5 - 1TB - USB3.0
I’m very much happy with this device! works perfect! However I have a problem…

But first of all description and a bit background:
I partition this hard drive like that:

  1. boot partition with Windows 7 installation files (for installing Windows 7 from USB to any machine) = 4GB (NTFS)
  2. Ubuntu with Grub2 - 20GB + 3) 1GB for Swap area (ext2)
  3. DATA = rest of the disk (NTFS)

The problem:
each time i plug in device it of cause appear as 2 drives (Win7 setup and DATA) I dont want that! i need hide “Windows 7 installation” partition that its never apear whenever i plug it in in any PC, but this partition is boot, so i cant hide it easy way! i launch my Ubuntu and run “Gnome Partition Editor” and set there additional flag to existing boot as hidden. but it didn’t work out, Windows 7 setup boot fine, but fail during installation because couldn’t read from hidden partition. ok i unhide it and left just as boot

than i try trough windows and diskpart:
select disk (nr of my disk)
select volume (nr of my volume)
automount disable
automount scrub

however it didn’t demount my “Windows 7 setup” and didnt delete letter.
when i plug it in back this partition apear again so “automount disable” didnt work also

I also read about GPT attributes: 0x8000000000000000. Specifies that the partition will not receive a drive letter by default when the disk is moved to another computer or when the disk is seen for the first time by a computer.
( official Microsoft source)  but im afraid that fallowing zeros after 0x8 are not zeros, they should contain rest information such as File system info (NTFS) accoriding to WiKi source

Could you please help me to explain how to hide botable partition without damaging it?

Best Regards

Hey? why nobody replay to me? it so easy question, how to restrict partition to be monted each time i plug in device?

im sure there is easy solution…