JunkExtreme has posted an article about the product activation feature of Windows XP.
The first problem with this feature is that by tying your hardware configuration to your product ID (PID), you won´t be able to install the software on more than one PC at home. If you were used to installing Windows from a single CD onto 2 or 3 computers at home, you will now have to purchase a copy of Windows for every one of them. However, Microsoft can justify this by saying that you bought a license for single computer so the fact that you can´t install the product on more than one PC at home is normal. Ok, but what if tomorrow you decide to upgrade your PC? Like buying a new GeForce 3 video card and add more RAM? The software would detect the hardware change, a different number will be generated based on your hardware configuration, and the next time you try to activate your product, you will have a bit of a problem. First of all, you won´t be able to activate online, because Microsoft´s Product Activation center will detect that your PID is already tied to another hardware configuration. Microsoft says you will then need to activate by phone and explain to the person at the activation center you upgraded, and in most cases they will allow you to activate on your new hardware configuration. Even the slightest change in hardware can cause this problem. Users have reported that adding more RAM to their system required them to reactivate Office.Read more