I have 2 computers, one with Win7 and one with WinXP OEM. I'm thinking of upgrading the WinXP OEM edition to Win8 Pro and transfer it to the computer with Win7, and then transferring the Win7 copy over to the (formerly) WinXP one. Is this possible?
No you cannot do this.
To buy the offer, you need an eligible PC (Windows 7 PC (except Starter) purchased between 2 June 2012 and 31 January 2013). After you have bought the upgrade, you can apply it to any PC.
The original license and the upgrade license combine (temporarily) to form the Windows 8 license, thus you can no longer use the original license.
You cannot transfer an installed copy to another computer. To transfer a license, you uninstall it on the original computer, and re-install on a new computer. However, as soon as you uninstall, the original license (XP) and the upgrade dissociate again, and the upgrade can be reapplied to any other computer.
The original license (XP OEM) remains tied to the old computer. Therefore, if you want Windows 8 on your new computer (using up the Windows 7 license), your old computer will have to remain on XP.
ZDNet explains the Windows 8 upgrade license clearly in How the new Windows 8 license terms affect you.
In particular, here are some useful points:
Notice the words you can remove the Windows 8 upgrade from an original PC and then install it on another PC, assuming the new PC has a license that qualifies it for an upgrade. While you can transfer your upgrade license, you cannot transfer the underlying OEM license, meaning that the new computer must have its own valid underlying license, whether it is a retail, or its own OEM license.
You can upgrade any Windows version to Windows 8, that's not the problem.
However, under no condition can you transfer an activated license from one computer to another. That will only get your Windows serial blacklisted by Microsoft, so lost forever.
The only way this can be done is with the help of Microsoft Support by phone, explaining to them the situation and asking for new serial numbers for the two computers.
However, as one of the licenses is OEM, meaning attached to a physical computer, and that upgrading to Windows 8 does not change its OEM status, I do not believe that Microsoft Support will agree.
But that doesn't mean that it's not worth trying.
Yes you can upgrade the OEM version of XP to Windows 8
From the microsoft blog,
Thereby you can install it on another pc.
If windows 7 is retail, you will not have any problems re installing.