Interesting. Tom's, do realize that you need a licensed copy of windows to run in virtually (according to Microsoft). I assume with the tiers that support XP Mode the cost of an XP license is built in - but for the other versions with this work around, I suspect that would be the equivalent to pirating a copy of XP (unless you buy a copy - at which point I'd say use VMWare instead).
[citation][nom]ProDigit80[/nom]Question,Is it possible to use an existing XP OEM CR-ROM to rebuild a working version, or use the license key of a version of XP that you already own?[/citation]
Depends... if you are talking about an OEM license that came with a name brand computer, you are out of luck (dell, etc). I tried virtualizing a copy of a Gateway, replace the OS with linux, and then use VMWare player to reinstall the OS on the same computer. Since it is keyed to the specific hardware, it did not recognize it as the same computer due to hardware virtualization. I am sure there is a crack or work-around somewhere out there I don't know about, but I was too lazy to find it.
A regular OEM copy if uninstalled may require calling up Microsoft to activate and stating that it is only on one computer. I constantly upgrade my hardware, so I have to do this about every year or two (typically when I replace the motherboard). They ask if the copy is only on one computer, which "yes" is my answer. Further inquiries and I explain I upgrade my hardware a lot as well as wipe and reload my entire OS regularly. Of course, Acronis Workstation has reduced this (as other imaging software would also).