Q: I am wondering how I can reformat my Windows XP partition on a dual system iMac without loosing the Mac side.

A: Apple has made it extremely easy to delete Windows partitions from your iMac’s hard drive in Mac OS X Leopard.

Open a new Finder window and go Applications => Utilities => Boot Camp Assistant. This will start an interactive wizard. In the wizard, choose the option called Create or remove a Windows partition. Follow the resulting instructions to delete the Windows partition from your iMac, and then restart your computer.

Enjoy!