The part that simultaneously crashed every other program running?
The part that added about three dozen new programs at startup?
Or maybe it was the part that took over my internet explorer, reset my homepage from "about:blank" to AOL.com, turned off my Yahoo! toolbar and replaced it with its own. And oh, thanks for reseting my IE toolbar settings from their carefully sculpted one line back to the default settings. I'm eternally grateful for THAT one.
Oh, wait, I know... the optimized part must be the part where it installed 50 million icons EVERYwhere faster than ever before. No, seriously, I just went to the bathroom, two AOL icons fell out of my boxers. AND I'm pretty sure I just burped up an ICQ one.