Depending on the version of OS X you are using formatting the drive using exFAT will work as well and will allow for storage of files over 4GB in size. If I am not mistaken some older versions of OS X may only give you the ability to read drives formatted as FAT32. You would, as was mentioned by Reyaz123, need to move data off of that drive before you format it. I have a couple of external drives I formatted using exFAT and they are easily read by both the Mac and the PC.