[quote=Prince of Seraphs]
But the ancient weapons platform was destroyed. What happened to the ZPM previously powering the drone chair?
[/quote]

No, the [i]chair[/i] was destroyed. The platform itself is still operational. 

Besides the chair is made of metals and such, as McKay so delicately puts in the episode where they are at the fake SGC ZPMS can't be broken easily, without some kind of mega explosion. The ZPM likely would of survived the Kamikazee.