I did my share of quality assurance for software products in the past (mainly dull things like specialized CAD packages or e-mail handlers) so I know how sometimes things can slip through but this one takes the cake.
EVE Online, the massively multiplayer online game where they don't even bother trying to pretend it's not work, released a new patch that is something really special. When it installs it deletes c:\boot.ini which has a bad tendency to make Windows XP very unhappy the next time the computer is restarted. Forced system restorations are running rampant. Apparently the game uses its own file called boot.ini (small tip for people writing software: don't name your files the same as OS system files) and someone left out the path in the installer.
This isn't the first time I've heard of a poorly QA'ed installation process overwriting things that it shouldn't but it takes some real effort to break a Windows installation and not notice (insert joke about all Windows installations being broken to begin with here).