This can possibly be because at one point you tried to install 3rd party bootskins to change the look of your bootscreens. A program such as Stardock's Bootskin can easily do this for you. Although when you quit using it I noticed that it had done the same to me as well.. I was due for a reformat so when I did that I fixed it.. I believe that if you just re-install WindowsXp it will fix the problem.
Hope that helps.