After Nero was imprisoned, why didn't the Klingons dismantle his ship?
That's a whole can of works right there that has been debated constantly these past three years. A recent issue of IDW's ongoing series even made a joke about it. Although IDW also attempted to explain it with their Nero series back in 2009. The less said about that explanation, the better. It involves the Borg and V'Ger. Seriously.