Here's a way around the conundrum, but it may be too involved for your bro.
  1. get an iPod and connect it to your Mac in disk mode.
  2. copy the mp3 files onto it in the Finder.
  3. send iPod to brother.
  4. tell brother to plug in iPod before installing software (so it will automatically use disk mode on his Dell -- hopefully it's running WinXP)
  5. copy music from iPod to hard disk, then delete it from the iPod
  6. disconnect iPod
  7. install iPod software and iTunes and reboot
  8. plug in iPod -- it will launch iTunes then ask to be associated with his computer
  9. add the music to the library
  10. sync the iPod

This is the easiest way I know to get the music onto his computer and still allow him to modify the contents of the iPod from his PC.