Guess, it depends on how badly someone wants to get those files back.
Let's say the NSA is about to find the location of Osama with one of those files,.....well I'm sure they would get back every and each piece of it.
The most effective way to erase files would be an eraser that uses the DoD standard (something like overwriting the file 15-20 times). As for deleting them with LW, for just the normal user they're gone unless you try to retrieve or restore them in a timely manner with some recovery program.
In general, with computers there seem to be no absolutes........
