Windows 7: Installing Windows 7 64 on USB disk

Hello,

I'd like to install Windows 7 64 on my external SATA disk (plugged via USB).
On this laptop EFI is enabled, and the internal disk (an SSD one) is using GPT and contains a single partition for a Linux system (other than the GPT system partition).



On the external disk I want to install Windows 7 and other systems (at least a couple of Linux distributions and an Hackintosh OS X). I'd prefer using GPT also on such disk, and want to be able to run Windows both natively and in VirtualBox.

How can I install Windows 7 on the external drive? Couldn't find many guides on the topic.
Also, would it be possible to install Windows 7 online from my Linux system (for example via VirtualBox) so that I can do it with the aid of a connected web browser?

Thanks!

That is only possible with an Enterprise license. The problem is not the installation, but the activation.

Uh, well, good, my university department provides Windows 7 64 enterprise (and, I guess, the server necessary to activate the system).