Hey,
Just thought I would come back and say that I was successfully able to flash, undo, reflash, re-undo, and flash again, my WD1200BEVS hard drive, and I have it working in my xbox 360. I used hddhackr v 0.91B and it worked flawlessly. I'm not too sure what SATA chipset I have, but I have a dell inspiron 4700 and it has an intel 2 port S-ATA on it, and it worked great. The only problem I am having is with transferring my old save data, to my new drive, but I think I am on the mend. (tip, turn OFF UAC in Windows Vista to copy files back and forth from hard drives).