Well, To change the boot screen, you first need to download appropriate boot screen from the personal website. There are lots of bootscreen in different websites like themexp.org. First download those files from there. The names of all the files will be like ntskrnl.exe. Just backup the original file from your windows/system32 directory. And just paste it there. Or you can rename the new file just downloaded to another name, say abc.exe. and paste it to the windows/system32 directory. If the file name is changed, you need to add an entry to the boot.ini file. Just open my computer and type c:\boot.ini in the address bar. you will be given with a text editor. just in the last line paste like the following..
multi(0)disk(0)rdisk(1)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect /NoExecute=OptIn /KERNEL=abc.exe