What I used

Installation

Make 2 partitions on the Hard Disk, say disk0s1 and disk0s2. Active the first one.
Install Windows XP on disk0s1.
Boot with PQ magic CD, active disk0s2.
Boot with iATKOS DVD
After seen the Mac OS Welcome screen, do not click Agree, click Utilities > Disk Utilities on the Apple bar at the top of screen.
Select the partition disk0s2, change the format of this partition and erase it. Quit Disk Utilities.
Go back to the Apple menu bar and select Utilities > Darwin_Boot
Type Y (yes) to contitue, type 1 for Hard Disk number, type 2 for the partition number, so that's disk0s2.
Type Y to install boot efi if the CPU is Intel Dual Core. Quit Darwin_boot if no error message.
Read the Terms & Conditions for iATKOS v1.0i and click Agree.
Select packages you want to install, I only select

MBIOS.KEXT.NETKES
REMOTE.APPLE.NEL.CPU.POWER.Management.KEXT 
and driver for the graphic card. I didn't select a driver for network card.

Now the installation of Leopard begins, it needs 20-30 min. After all of these, you can use Leopard, but you can not get into Windows XP.

C:\chain0="Mac OS X Leopard"

Reboot, now you have a menu with two options, one is Windows, one is the Leopard, after selected Leopard, you have to click F8 to enter the system.

Don't change Hard Disk Partition Map with Disk Utilities (from iATKOS DVD), Disk Utilities can only be use to change the partition format and erase partition.
If one operation system can not be booted (like the blink cursor error), normally you need to active the partition of system.

If you don't have PQ magic, it's also ok, you can type some commands mentioned in other manual.