Choking a computer refers to the process of holding down the power button until the given computer manually shuts off about 5 to 10 seconds later (presumably "choking" because of a loss of power). Not the preferable thing to do when working on one, as it loses all unsaved data in the process... However, one of the only things most Microsoft programs respond to.
Dang it! Windows XP just froze again for the (insert 4 digit number here)-th time today! Time to choke the computer again... *sigh*