[ubuntu] Installing issues from External HDD

Hello people, I have a simple problem but I still didn't get any efficient solution for it.
So, here's what I have :

- External HDD
- Ubuntu ISO file
- Windows something ISO file
- A PC with Ubuntu system
- A PC with Windows system

I want to install Ubuntu on the PC with Windows OS, and I want to install Windows on the PC with Ubuntu system. Without flash, without CDs.

Is it possible? and HOW?

any helpful ideas?