OK, for the guys asking about the Asus drive, I have created a crossflashing pack for you because I noticed when I did mine last night that the information and tools were conflicting across multiple sites and someone with less experience than me could easily brick the drive.
Pack is
HereThis was tested on the DRW-24B1ST but I see no reason why it shouldn't work with the other MTK B-chipset models as well and contains the stock AL18 iHAS324 firmware. If you want to the take the drive to another model like the 424, 524 or 624 then this is also possible and will just need the correct exe flash file for that drive.
Process is:
1. Launch EEPROM utility and backup EEPROM.
2. Launch Firmware utility and backup Firmware.
With the above steps, these dumps will be needed if you ever need to return the drive to stock for warrantee repair etc so it's a good idea to make 2 dumps just to be sure.
3. Flash the drive using the Firmware utility by selecting the included exe file (or another one of your choice). All settings should be left as default.
4. After the Flashing utility confirms that the flash is successful, power cycle the drive. The Green activity LED on it will now flash constantly but the eject button etc should respond as normal.
5. Run the EEPROM utility and launch the Convert option. This will finalise the crossflash process.
6. Once this has completed successfully, power cycle the drive again.
7. The drive will now be recognised as an iHASx24 B model and the process is now complete.
I flashed my drive using a laptop and the X360USBPro and this worked perfectly. I then tested it after the flash by burning an XGD2 title, again through the X360USBpro, and which also worked flawlessly although the firmware forced 4x on Memorex media for some reason.
My drive was manufactured in July 2011 but I have seen elsewhere that drives going as far back as June 2010 still use the MTK B version chipset so there should be plenty of these around.