Well basically the boot video that plays by default is located in here:
/usr/share/MProgressIndicator/themes/opengl/MainAnimation_LowNoise.mp4
One way you can do it, manually at least, is to take a video you want to use, rename it to MainAnimation_LowNoise.mp4, then simply replace the original with the new one. If you're unfamiliar with terminal commands have a look at the code contained in the first post of this thread: [Announce] Custom MeeGo bootup video
The only thing that may not be completely spelled out is that when you open the terminal you should type "devel-su", then "rootme" as the password (assuming you haven't changed the password for it), it gives you root access so you can manipulate files / folders etc that a normal user possibly shouldn't, after getting root access you can do the commands described in that first post. That's what he's getting at mentioning SU.
Cry out, if it still doesn't make sense, can go deeper into it, I think you'll be alright even if this is all new to ya though.
I'm pretty sure there was something done for removing the nokia text with the pulsing circle etc, but I like it, hence never tried to modify that and I can't remember what thread that was covered in, I could be wrong about that being done mind you.
