It only takes 6 steps to make a bootskin
1)make the background graphic: has to be a 640x480 pixel, 16 color (4bit) bmp.
2)make the progress bar graphic: has to be a 22x9 pixel, 16 color (4bit) bmp with the same color table as the background
3)copy a bootskin folder already made in the bootskin directory and name it what you want, delete the graphics in it and copy/move your graphics into it,
4)edit the ini file in the folder so the graphics are set to yours, and the location and width of the progess bar is correct
5)load up your bootskin and check if it works by restarting your computer
6)if not right edit graphics or ini until it works
I don't see why we even need a tutorial. bootskins are really easy to make, if you just look at one bootskin in its folder you see how its made.