Pretty shallow trees (1 level, a few subdirs, a few thousand files total) and the operation only happens once per run (a run may persist for hours to weeks or possibly months), so this does not need to be optimized at all. I was more concerned about heading off any "why doesn't your code work on my non-*nix OS?" Will trade processor cycles for programming cycles here, I think, and avoid having to know about all those DOS /flags, and similarly for any other OS somebody tries to use.

But that sort of thing--dropping to the system level for intensive file management--is good to know if I need increased performance for similar tasks in the future.