Actually, MrMister is right. Every time the system tries to open a file ShapeShifter will add the overhead of actually checking to see if it's a file it's interested in, even if it doesn't actually need to patch the file. The penalty is not huge, but you're probably about doubling (edit: now that I think about it, the changer has to search some database of files it's interested in, which depending on the algorithm, would probably be at least triple or quadruple) the time it takes to get a file open for reading. This isn't noticeable under most cases, but from a strictly computer science standpoint, that's a decent speed hit.