A mate of mine asked me to do this, but my experience of Apple machines being somewhat incomplete, I wasn't able to help. From what I can assume, I'd need to boot from a CD or whatever and do it from there in single-user mode, but I've only ever formatted a *NIX drive during automated setup so I'm not sure of the commands. Then again, if he wants to format it, it'll need reinstalling, won't it? So he might as well just repartition it as part of setup?

What do you think?

You can repartition the Leopard HD with the setup disk I believe. You can also do it as part of Bootcamp as all that does is resize and repartition the existing Leopard HD and leave it ready for Windows setup to format.

Boot the DVD installer, and then click on Disk Utility in the Utilities menu.