User error, really, though I'm puzzled as to how this is doable with an OS X installation, since the OS doesn't suffer many of the architectural flaws that puts Windows in these situations. I've been running (and maintaining for others) OS X for 10 years and Windows for 15 years, and with OS X installations I've never seen this occur. For what the anecdot is worth my own Windows installations have always stayed healthy (and just noticably sluggish) even after years of use.