Windows 7 Key only works with 32 bit, not 64 bit?

I've just installed Win 7 download upgrade a second time (both times as a virtual machine in vmware), as I wanted to check the activation workaround here:
http://community.winsupersite.com/bl...he-answer.aspx
It happily authorised. I quit and reopend my first install, and that's still authorised.
Could be because the hardware still matches, or maybe because of the workaround?

Clarification: You can only use the retail key on one installation at a time. The license belongs to you for life and can migrate as often as you want, but only on one machine at a time.

With Upgrades it is a bit more complicated: the key becomes tied to the underlying OS, which if it is OEM means tied to the motherboard of the one machine, or if the underlying XP/Vista is retail then the Upgrade is also portable and can migrate freely with that XP/Vista retail copy - but just on one machine at a time.

Now, here's the topper: MS Technet gives the above EULA, but admits they have no way to enforce any of this except the "one machine at a time" which they do track closely, so the Upgrade can functionally migrate to any machine whether OEM or Retail, just one at a time.