Change volume licensing product key in Windows product key

If you are using product key that is being used several times and finally you end up getting invalid product key or you might not be able install sp1 or later version of Windows XP.In such case you need to play with registry which no one can take risk but kb article-328874 might help you much better to change volume license product key with step by step and more precise.

Link to change Volume Licensing Product Key