Many "discoverer" tools also allow users to update or change the product key without a full reinstallation. How to Use Product Key Recovery Tools
Some versions can point to a specific [Windows Directory] on a non-bootable hard drive to pull keys from an inactive installation. Xp Key Recoverer And Discoverer 5.12
Run the utility with administrative privileges to ensure it can access the protected registry hives. Many "discoverer" tools also allow users to update