My sister's 500GB external hard drive was NTFS formatted, so her Mac OS X couldn't write to it.

I saved her data somewhere safe, ran "format E:/fs: FAT32" (just to see the error I'd get), only to get "The volume is too big for fat32". (Not suprising, given the many limitations of FAT32 on XP)

I fired up SwissKnife (which comes with a BartPE plugin), formatted the whole thing with FAT32, then dumped her data back on. (Fortunately there were no files bigger than FAT32's 4GB limit)

It's really quite a cool little formatting tool. It's features include:
  • Formats faster than the OS (click on chart for details)
  • Allows change of cluster size during Full format or Quick Format
  • Divides a single hard drive into one or more partitions
  • Supports Hi-Speed USB, PCMCIA, SATA, SCSI, USB 1.1, and FireWire® external drives
  • Supports Fixed and Removable disk formats
  • Supports FAT, FAT32 & NTFS systems
  • Allows creation of a single partition of up to 2048GB of FAT32 or NTFS file systems
  • Full format or Quick Format of existing partitions
  • Selective partitions can be modified for optimum flexibility

I'm curious as to how they format FAT32 drives up to 2048GB in size. They answer it in this FAQ, but they don't tell how they do it.

Note: if you use the BartPE plugin, note that the safety lock is removed, and you might accidentally create or delete partition on the drive OS is installed.

Update: for those interested, here's what I did to quickly copy everything back to the original drive:
c:\sisHDD\xxcopy *.* /s e: /y

And to quickly strip out any stupid attributes that might make it difficult for her to work, I ran:
attrib e: /s /d -r -a -s -h

Update: Here is more info on MS file systems.