I have no doubt this is a stupid / simple question but anyway...here goes. I bought a portable external hard drive for work and backup, so I'd like to take copies of files home from work. My work machine is a PC, Windows XP I think, I run OS 10.3.8 at home on my mac. Initially I formatted my drive using the disk utility on my mac, and I formatted it as DOS. My Mac and my work PC could read and write to it. However, I thought instead I'd format my portable drive on my work pc (just out of curiosity I guess). Now when I brought it home my mac can read the drive, but not write to it. Can anyone recommend a decent format solution? Should I just reformat it as MS-DOS on the mac? I definitely want to be able to use my drive on both operating systems. Thanks.