Just throwing my two cents in. What if Desmond wrote the "Subterranean Conduit?" on the wall. Desmond might have also noted that you couldn't journey very far from the computer because of the 108 minute deadline.

And what about that telescope thing Desmond used at the start of the season when they blew the hatch.

Also, I wonder if those "X"s at the ends of the tubes aremeant to show that they have been sealed off--in concrete. Could Dharma have tried to turn the Hatch into a doomsday bunker because they thought the staff people (Dharma personnel) were infacted/contaminated? Hence the vaccine that Desmond was injecting himself with. Also, the reason why the Others felt it necessary to innoculate Claire's unborn child.

And wouldn't that explain the Others' attitude with "taking" only the best survivors? They've been left to fend for themselves by Dharma, with only the resources of the other two stations.

And, finally, is it possible that it was Walt who got the computer network up and running again? The Others did not have the expertise because Dharma didn't want to risk contaminating the clean areas of the island (or the healthy personnel) to help them fix it.

__________________
charlie98210
"Whoa!" she said. "Cry 'Havoc!' And let loose the dogs of war!"
And, like Banquo's ghost, they just won't go away.