the problem with ubcd4win is its so old and relies on XP. Some newer laptops dont even have xp drivers and ive been unable to see drive because of this.
That being said I still carry a flash drive with it, and while windows can be installed on an external esata drive, or USB with some hacking, it would be illegal to move it around to different machines, would have constant driver problems, and would constantly be trying to reactivate and get the key locked out very quickly. So not worth it. use ubcd4win or a Linux live CD.