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This guide will teach you how to flash/flex your phone using Flash & Backup 3.
Things you will need:
Before flashing ANYTHING, you should ALWAYS ALWAYS ALWAYS make a backup of your stock files. This way, you are able to revive your phone if you brick it. A full backup can be acheived by using a REGISTERED version of Flash & Backup 3. In order to register it, you must visit http://www.motorola-tools.com/index.php and purchase your copy of FB3.
I will be flashing InsecureSpike's Remix DRM. Once you have all the files that you need, power on your phone in Bootloader mode. (# and * while pressing power)
Open Flash & Backup 3.
1. Make sure your Active phone profile is Motorola RIZR_Z3
2. Also make sure you are on the Write Data screen
3. Once the first two are confirmed, choose Select File.
Navigate to where you saved the SHX file to be flashed. In my case, I saved mine to the desktop so I could easily find it later.
Once you select it, you will have a screen like the one below. If you're flashing a drm, there will only be one thing in the red box that I've made. Now select Write Data from the bottom right corner.
Flash & Backup will begin the flashing process. You will get a screen like this one while it's flashing. Depending on the size of the file you're using, this screen may stay longer.
Once you're done, Flash & Backup 3 will say "Operation Done" and you will be able to close the little window.
Now for me, when it's done flashing, my phone just shuts off. Yours may restart or just shut off like mine does. Just turn it back on and you should be okay.
That's Flashing/Flexing in a nutshell.
Just a sidenote: Most K1 fonts and DRMs can also be flashed to the RIZR Z3.