I tried MicroXP. I love it but I don't like that the image at the top of Windows XP login box is replaced by an image that says "MicroXP".
If you are using MicroXP and would love to remove the "MicroXP" image and replace it with the default image,
Here's what you should do.
1) Download the original msgina.dll.
2) Replace the msgina.dll in the \WINDOWS\System32\ folder with the original msgina.dll (the one you downloaded)
If you want a custom bmp, you can use ResHack to modify msginal.dll