So what do you do if you’ve totally screwed up your system software on your GSM Nexus device? You need to flash a factory image to get back to stock, and as luck would have it, Google has released the official 4.0.4 (build IMM76D) factory images for the international GSM version of the Galaxy Nexus and the European and T-Mobile unlocked Nexus S. Flashing these files will leave your phones as if they were brand new and completely updated.
Flashing a factory image requires that you are not shy around a command line and fastboot, so it’s not for the faint of heart. If you’re brave and own one of these Nexus devices, download the images at the source link below.
source: google groups
via: androidcentral