I have a Windows XP computer with USB 1.1, and a Mac Mini that has USB 2.0 and Firewire 400. If I get an external USB HD, then I will have to format to FAT32, but I can connect to both computers. On the other hand, if I get a Firewire 400 external drive, then I can only connect to the Mac, but I can format to HFS+. Now, the files on the drive will primarily be documents and other files, so no programs at all will be on it. I am unsure as to how often I will need to share files between the computers. What are the advantages and disadvantages of FAT32 and HFS+, and USB vs. Firewire as well? I want to decide which format I should use Thanks!