i believe the problem jmcjmk, is that in the boot up phase windows is not yet in charge of graphics. the operating system is not loaded, the video drivers are not loaded, the hardware acceleration that is needed is not loaded. the 16bit graphics which microsoft uses for its boot screens are no different then the graphics your bios displays when you first turn on your computer, or the 'HP', 'Dell', or 'gateway' splash screens when yuo boot up that hide the memory checks and hardware detections of every boot.
on a mac system, the operating system has that control of the graphics once the power is on, so they can do sharp boot up screens. that type of control would have to be added into your computer's bios, and the freemdom of a pc - using any random hardware you want - makes that impossible. windows may, in the future, include that type of control from the getgo, but i'm afraid it won't happen under XP.. unless, a program is developed to drive your graphics outside of windows.
as usual, if i'm mistaken on this process, someone point me out.. but from what i know of dos and the windows/dos/bios hybrids this is the best explanation.