So a app has been put together to make this very easy now. If your into changing out the M logo on your X then this app is worth the .99. Not only can you pick from a growing online album you can also create your own and drop them on your SD card to install. I love making these and can now skip a few steps when doing so. Check it out!
DROID Boot Logo Changer Released, Customize Your DROID Startup Screen - Droid Life: A Droid Community Blog
DROID Boot Logo Changer Released, Customize Your DROID Startup Screen - Droid Life: A Droid Community Blog