If water gets on the components there's always going to be a chance of damage, no changing that, and the likely hood of damage if you use deionized water instead of plain distilled is only slightly less. 'Course, if it's only a couple drops it probably wont hurt anything, and if the pc is off when the leak happens, as long as everything is dry before turning the pc on, everything should be fine. Like I said, if you can find the stuff, use it, but don't go out of your way to get it. The only 100% safe liquid to use in wc'ing is something like ultra pure mineral oil, which is used to cool and insulate high voltage transformers and such.