electro you could crossflash your OEM drive to the "B" firmware. download the WinDXFLASH.exe file & B7P9 cvt file from this site: http://dvdpro.club.st/firmware/BENQ_FW.htm
if you want you could flash the drive in SAFE MODE. make sure the drive is empty when flashing, turn off any software that is running in the background such as antivirus. then double click on the WinDXFLASH exe file, it will ask for the firmware and just direct to where ever you have the B7P9 CVT file. Reboot pc when it's done flashing. then go to device manager and you will see the drive read BENQ. you will then be able to use any official firmware that BENQ has such as the latest B7V9.
to Ma_Jie: Chill out with the do the forum search. it would have helped if we had a FAQ in this BENQ FORUM then there wouldn't be people asking the same questions over and over. I know the FAQ is in the works so we should be patient with others when questions are asked