Gary has an iMac, and there's a large percentage of JPGs he can't preview. What is that all about? Leo says if the dimensions read "0" by "0", then the Mac thinks that the files are damaged and need to be repaired, even though Gary can read them on a PC. He should try opening them in Preview first. If he can read them there, then he can export them. Gary can also open them in Picasa, and so Leo suggests exporting them out from there. That can fix them and the Mac apps should be able to open them from there.