New
#41
If you have a retail copy of Win7, then you CAN use the license on "another machine", but of course only one machine at a time.
That's why you phone MS when the activation wizard complains, on the phone number they provide. You will then go through the automation to enter the special key they have put on the screen. The automation may or may not now accept your entry, or will put you in touch with a human to whom you'll explain your story, that you upgraded hardware from a dead machine and never had a chance to uninstall/deactivate your retail Win7 license for that other machine. But it's no longer in use, and you now want to activate that license for the new current hardware.
They will make the swap for you, on the phone.