But...XP usually pukes when it finds new mobos and CPUs thus requiring a reinstall...which will probably mean activation, and possibly validation.Should work fine without need for re-activation
From the Microsoft website
Microsoft defines "substantially different" hardware differently for PCs that are configured to be dockable. Additionally, the network adapter is given a superior "weighting." If the PC is not dockable and a network adapter exists and is not changed, 6 or more of the other above values would have to change before reactivation was required. If a network adapter existed but is changed or never existed at all, 4 or more changes (including the changed network adapter if it previously existed) will result in a requirement to reactivate.
Scenario A:
PC One has the full assortment of hardware components listed in Table 1 above. User swaps the motherboard and CPU chip for an upgraded one, swaps the video adapter, adds a second hard drive for additional storage, doubles the amount of RAM, and swaps the CD ROM drive for a faster one.
Result: Reactivation is NOT required.