I've got several legitimate Windows licenses. I tried to install it on my dad's computer but I had to leave before the installation completed. I returned a few days later to activate it but somehow a virus managed to infect it. I removed the virus, but Windows just refused to activate with a LEGAL KEY. I tried activating by phone and I received an activation key but it didn't work either (permissions error or something). So I just did the sensible thing and installed a version that I found on TPB.

Seriously Microsoft, drop the activation scheme. It's not necessary and causes nothing but frustration for your end users.