Hi,
I am new to flashing but my box was already flashed to 5.3 by a friend.
I just picked up the 1.2b FW myself this time and have iPrep ready with the corresponding xml.
I have an Asus P4V800-X with 8237 southbridge and thus a matching SATA onboard controller.
As stated in the iPrep tutorial, this should be supported in one form or another:
# Via 8237
# Some 8237 will sometime appear as DUAL Standard IDE controller
However, this is not the case for me...
When selecting custom I get the VIA bus master IDE controller as default and can also select the primary IDE or Secondary IDE. None of these are supported by MTKflash (message appears when either of these 3 is selected)

I have nothing attached to the SATA ports at this time as my Boot Hdd (and all other Hdds) are connected to my P-ATA connectors.
Is this where things are going wrong or is it that the onboard SATA is not supported?
Do I have to connect the 360's drive tot the sata port while prepping the USB? That would not seem very logical to me...
If anyone could help, it would be much appreciated!