Elsewhere in the hatch-hole, Locke is explaining to Desmond about how the plane was a thousand miles off course when it crashed, so any search parties, which would have given up a long time ago anyway, would have been looking in the wrong spot. Locke's sitting by the phony sunlight.
Locke asks what Desmond's name is, and Desmond looks surprised, and then almost a little pleased, to be asked, and tells him. Sensing an opening, Locke tells Desmond that the gun is unnecessary. Opening closes. Desmond points it at him and sarcastically asks if he should just hand it over to Locke. Try saying yes again, Locke. It might work this time. "How many of you are there?" asks Desmond, after he cools off slightly. "Forty-three," says Locke, adding that four sailed away on a raft this morning. Desmond chuckles at the idea of leaving by raft. Locke asks about the simulated sunlight: "Is that because you never leave?" He asks if there's another way out, but instead of answering either of those questions, Desmond asks how many of the group are sick.
Locke doesn't seem to understand the question, so Desmond has to snap, "As in ill! As in dead!" "Is that why it says 'quarantine' on the inside of the hatch?" asks Locke, and Desmond tells him to just answer the question; the answer is no one.
Then the beeping starts. The biker gang pirates are sailing down the hatch-hole? Up in the air duct, Kate hears it too. Desmond tells Locke to get up, and they go into the room with all the ancient (well, '80s, anyway) machinery. Pointing to the computer, Desmond asks Locke if he knows how to use it. Locke says he hasn't seen one of those in twenty years. Locke, next time someone asks if you know how to use an old computer? You say yes! Actually, that's exactly what then happens, with Desmond's rifle used as an exclamation mark. There's a timer on the wall behind the computer, reading 00238, with the first three digits in white numbers on black, and the last two black numbers on white. Looks like minutes and seconds. Desmond tells Locke to enter exactly what he's told and nothing else. Then Desmond starts listing the numbers: "Four, eight, fifteen..." Desmond's momentarily distracted, asking if Locke heard that (I didn't hear it). Locke didn't. Desmond finishes telling Locke the sequence (how freaked out would Desmond have been if Hurley were there and he guessed the rest of the numbers?), then orders Locke to hit the EXECUTE button. Locke hesitates, presumably worried about what might happen when he does, but then hits it. The beeping stops, and the timer resets to 10800.