I would just like to point out an application that i myself had come across recently to retrieve my Windows product key and MS Office keys.
XP CD-Key Finder: by Mayhem Development
This application i found very handy and very quick to use, Plus it allows me to use it at work for the more difficult job of trying to find the cd keys on a non-bootable hard drive.
Basically it will get the product keys as per usual but will also obtain the current IP/User/PC Name which saves me just that little bit more time when i am doing multiple computer.
I have put it on a USB key which i quickly just plug in any time i need to use it.
But the better part is it is now on my main pc... If i cant boot a hdd i will simply plug the hdd into a usb adapter and then run the application on the ntuser.dat or the *.sav files which has allowed me to obtain the keys that way.
Hope this one can be helpful for someone else like it has been for me.