use fastboot to change recovery.u can download cwm from rommanager site (M7), then, after power on the device in fastboot (vol down + power on), in cmd type: fastboot flash recovery "recoveryname".img (the name change on what you download. you are now good to boot into cwm recovery.
now you can sideload a rom from pc. in the recovery wipe data then select flash update zip from sideload and after downloading the rom you wanted you can type adb sideload rom.zip (rom name change on what you download). and bam you have flashed a rom from pc to phone and you could now reboot your phone...it's an international m7 so look for gsm roms only