My MacBook Pro is fairly new, but I have a 500g Western Digital external hard drive that was originally hooked up to my previous computer, a PC. When I plugged in my external, I was able to move files from it to my Mac. However, I was unable to delete files off of the external while it was plugged into my Mac and I could not add files, either. When I booted up my old PC and plugged the external into it, it worked fine. So I can only assume that since I first used it on my PC, I'm having trouble using it on my Mac. A friend of mine told me something about how I'd have to reformat my computer and start over. PLEASE tell me this is not the case. Does anybody know a way to fix this that lets me keep my Mac as is and not have to delete anything? Help would be greatly appreciated. Thanks!