When you try to install Windows XP for Boot Camp using Boot Camp Assistant, you are required to have a single partition to start out with. For those who already have partitioned their disks manually, this is truly inconvenient.
If you already have partitioned your hard drive, you need a manual installation method. Many of the installations with only one or two Mac OS partitions (in addition to Boot Camp) can be done by simply starting up the Mac with the XP installer disc and installing into the C: drive that it recognizes. (You will have to make sure the FAT partition is less than 30G, and that you do a Quick Reformat into FAT before install into C:). However, due to XP limitations, if you have more than two Mac OS partitions in addition to the Boot Camp partition (ie more than three partitions total), XP cannot handle it, as XP can only detect up to three partitions. If you try, it will force you to reformat the entire drive (including the MacOS portion) to NTFS ... and that is not good.
The way to get around this three-partition limitation in the XP installer is to trick it into thinking that the Mac OS parititions do not exist. For this, I found that if you use iPartition v3, you can make your Mac OS partitions "vanish." Launch the program, and in the partition inspector, uncheck the 'Viewable by Windows' box for all of the Mac OS partitions. Now when you boot up using the Windows XP installer, it will only see the partitions that were formatted in FAT (under 30Gb please!), and will lump all the other Mac OS partitions together as "unrecognized disk space" and ignore them.
This way you can have four separate Mac OS partitions (I have System, Applications, User, and EFI header -- which is created for all IntelMacs) and the Boot Camp (FAT) partition, and you can still install XP manually. Once you conclude installation, one step that I didn't see in other hints that stumped me (mainly because it's the RTFM issue, and was my fault) was that you can get all the hardware drivers installed by simply inserting your Mac OS Leopard installer disc after rebooting into Windows XP. This will activate all the Ethernet ports, wireless, display, sound card, etc.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20080213123408244