OK ... since you already created a partition for Windows on your disk, try simply installing Windows from boot. With your Windows DVD disk in the drive, shut down (power off) your computer, then turn it on while holding the "option" key down until the boot disk icons appear on the screen. Hopefully, the DVD will be at the far right side of the option icons. Step the cursor arrow over to the disk and press "return" to start loading.
If you are successful, the installation loader will start. When you are presented with a list of drive partitions, be sure to select the right one (should be labeled BootCamp) and then you must format it for NTFS from the menu options at the bottom of the list. Remember which disk/partition number you are on.
After formatting, again be sure the correct disk is selected. It will no longer be labeled BootCamp, but you can verify the disk/partition number from above, and the size to be sure the proper one is selected. Now continue the installation. It will reboot a couple of times to finish the installation. If the first reboot takes you back to OS X, simply select the windows disk in the StartupDisk preferences to lock it in as the boot disk, and reboot.
Good luck....
-howard