I love people who want to customise WIndows Vista and some of my previous posts have covered this, however you can go too far - you can hack the OS. While I understand the desire to "hack" the OS to get customisations, there are better ways. This particular example is where people want to change the boot screen in Vista. The ability to do this will be coming from StarDock soon, but until then people have taken to modifying the existing OS files. THERE IS ALWAYS a change that by downloading someones customised file to your PC and it being loaded so early on in the boot process that it could do nasty things, especially since these files are in now way certified by Microsoft. A classic example of this can be found here when people want to change the boot logo - this could easily be a social engineering attack. The instructions tell someone to remove the access and security permissions from a core system file, overwrite it with one that might make the system look prettier during boot, but who knows what else will...