How do you safely remove TNT?

Assuming GnomeSlice wasn't referring to himself in the third person as the 'friend' who did all this:

A more direct (but boring) question would be, how do you safely remove TNT?

Solution 1:

As of Beta 1.7, TNT can only be detonated by fire or redstone, meaning it is now possible to remove placed TNT like any other block.

Solution 2:

Note:

As of Beta 1.7, TNT can only be detonated by fire, redstone, and explosions, making this answer obsolete — recover your TNT as you would any other block.

For Beta 1.6 and lower:

While you can't recover the TNT, you can remove it safely with water. TNT which is submerged in water when it detonates will not cause terrain damage or trigger nearby TNT. Be careful however, as it will still cause player damage.

With this much TNT, I'd personally play it safe and drop a source block on top of each block of TNT before setting any of them off. Once placed, you should be able to remove all the TNT at once (albeit one at a time) without needing to introduce any more water.

I'll leave answering the follow-up question — how to remove all that water afterward — as an exercise for the reader. ;-)