Thanks very much to biktor_gj over at the xda-developers forum for discovering this method.

If you’re lucky enough to have one of the first batches of Nokia Lumia 800 and have only updated it using the Zune software Nokia left a present on the device:  Qualcomm Development Bootloader.

You can test for this by doing the following:

  1. Turn the phone OFF.
  2. Press and hold VOLUME UP + POWER until you notice a short vibration.
  3. Plug in to your computer via USB.
  4. If the phone turns up in disk mode (USB Mass Storage Device) then you have an unlocked bootloader.
  5. If you’re in Windows, it will ask if you want to format the disk. SAY NO OR IT WILL EXPLODE (it won’t explode but you might break it).
  6. If the device detected by the computer is Nokia DLOAD you have a locked bootloader and you’re out of luck.

I did all this and thankfully I had the Unlocked Bootloader, so here is my steps to installing the InteropUnlock Rom using Mac OS X:

Turn the phone off and hold VOLUMEUP + Power until you get the small vibration and then plug in the USB. You should get a NO NAME volume appear on your desktop if you have the Qualcomm Bootloader.

Open terminal and type the following:

cd /dev

Now look through the folders in there I had the following sequence, you should have something similar diskXs{1,9}:


I backed up the partitions using terminal again (repeat the command for each disk):

dd if=/dev/disk1s9 of=/Users/<username>/disk9

I got an error with disk1s4 as it says it’s in use, apparently this is the logical partition definition and so can’t be backed up.

The disk1s9 is 15GB so make sure you have the space before you back it up.

Once backed up I downloaded the new-os.nb to my /Users/<username>/ directory and flashed it to the phone again using dd in terminal

dd if=/Users/<username>/new-os.nb of=/dev/disk1s9

This took about 25 minutes. If you open a second terminal while the dd is running you can check the progress of the dd comand with the following command

killall -INFO dd

This gave me peace of mind as I could tell that it was still writing.

once that has competed do a hard reset and you should now be unlocked.  Hold Power button for 10 seconds to exit Qualcomm’s disk mode, and press and hold POWER+VOLUMEDOWN+CAMERA until you feel the phone vibrate. After that, RELEASE power button but KEEP HOLDING volume down + camera for five or more seconds. This will trigger the hard reset.

After booting up I had to Activate My Phone as other people have said I used the online chat feature here: General inquiries for home users I provided my phone number and they gave me an activation key.

The phone is working fine.