I'd like to have this My Password Essential external drive and my usb drive on both the Windows PC and the Mac. I have had them only on the Windows PC and have backed up a lot of files on them. I'd like to backup files on the Mac on these same drives and still be able to use them on the PC. Is there something in particular that I must do for that?
Use FAT-32 as the file system. Both Windows and Mac can read and write that without additional software.
Note: Reformatting the file system will ERASE all the data on the drive.