Please read http://support.microsoft.com/gp/pidwin. You probably won't be able to find that info as is in the registry.
http://www.dagondesign.com/articles/windows-xp-product-key-recovery/
Thank you. I did not know that it morphed from an 8 digit number to a 20 digit number. Is there a way (in the registry perhaps) to see the original PID with which windows was installed.
If there is no point in seeing it, why would it be heavily encrypted?
Microsoft paranoia? OK so there is a reason for wanting to see it but it's usually because people think they can crack it into an activation-free copy.