It's awesome Landshark.
The iMac will come preinstalled with OS X, but I'm not sure if it comes with Bootcamp. But anyways, you can download it off of Apple's site and during install it will give you the option of burning a disc with all of the Windows drivers that you'll need.
When you install Bootcamp it will suggest raping some hard drive space from the OS X partition to make a Windows partition, or you completely erase OS X and make a single NTFS partition with Windows if you wanted (I did this on a mac mini at work).
If you decide to dual-boot then you will see a new control panel in Windows XP titled "Startup Disk". This control panel is identical to the "Startup Disk" system preference in OS X where you decide if you want to boot to OS X or Windows. It will remember your choice everytime, so you won't see a traditional boot loader after POST.
I've been running a mac mini on Windows XP for the better part of a year, perhaps longer, I can't recall. It works fine, although you have to get used to right-clicking the CD/DVD icon in My Computer and then choosing "Eject" from the menu as none of the Macs have eject buttons on their disc drives.