What you can do is install Linux with VMware Player on all computers. Then install Windows under VMware Player on an external SSD (eSata or USB3 attached). Now you can run this Windows on any machine under VMware Player. In this case, VMware Player is the 'machine' on which you installed.
My Computer
Computer Manufacturer/Model Number
HP, Dell, Gateway, Toshiba - 4 laptops and 2 desktops
I think it is legal in so far as you can attach the external disk only to one system at each time. It would be illegal if you made multiple copies of the virtual system and ran those simultaneously. I use a retail license. With an OEM license that may be borderline.
My Computer
Computer Manufacturer/Model Number
HP, Dell, Gateway, Toshiba - 4 laptops and 2 desktops
It's not legal for the reason that it's not legally possible to install win7 to boot from external media. I admit that it may not be specifically excluded by the licensing conditions but it's been established that separate vm installs even on the same machine each require their own license
My Computer
Computer type
Laptop
Computer Manufacturer/Model Number
Asus K52F or Lenovo B51-80
OS
Win 7 x64 Home Premium (and x86 VirtualBox VM)/Win10
CPU
i3 370M/i7 6500U
Motherboard
Asus/Lenovo
Memory
8GB - finally :)/8GB
Graphics Card(s)
it's an i3, dude!/dual Intel&nVidia
Sound Card
onboard
Monitor(s) Displays
15.6" built-in
Screen Resolution
1366x768/1920x1080
Hard Drives
750GB Seagate internal
Sundry external drives attached to other computers on the local network
1TB SSD on the Lenovo
PSU
n/a
Internet Speed
as much as I can get - usually on a dongle/phone, so <1MB/s
It's not legal for the reason that it's not legally possible to install win7 to boot from external media. I admit that it may not be specifically excluded by the licensing conditions but it's been established that separate vm installs even on the same machine each require their own license
