Registry tweaks to try to make it faster, turn off services I didn't want or didn't use. Editting the boot up screens and the themes (without installing any other software to do so for you which then means more patching of files). As for how it screwed up, Windows update. (but like I pointed out, that's a problem you'll face with almost every system, Apple, Linux, Windows) There was something else I don't remember though that I didn't like about hacking around with Windows. I think it had to do with the different libraries.