Windows OEM Copies on mutliple PCs

No. You must buy an OEM license for each computer you build. To do otherwise is piracy.

... and besides, activation wouldn't work on the later installs.

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.

It's still not legal that way. Each and every install requires its own licence.

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.

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

NoelDP said:

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

That is correct. You need an own license for the VM installation.