Precision 690 A01 Bios not downgrading

Hello, i am in the hands of a Dell Precision 690, with all the normal stuff (including a duel core) which i want to change, i understanded there is a bypass for the DT029 motherboard not being compatiblewith quad cores if you downgrade your bios to A01, i have tried so mainy ways to do this, booting the update in windows, flashing it via usb flash drive booting and using DOSbox, nothing has surprised me, please help i have a quad-core sitting on my disk in its protective packet, just waiting to be used, i've tried booting on A02 with the quad-core in place but it doesn't allow it, how can i downgrade my bios to this using windows: http://www.dell.com/support/drivers/us/en/19/DriverDetails/Product/precision-690?driverId=R129239