Bb 8700

Hi All
I have a 8700 on Rogers network I tried to flash it with the newest Firmware which was the Vodophone firmware which messed up the screen. I tried to restore it but gave messages that some files were not restored so I downloaded the oldest firmware from Rogers and tried to restore it back, now all it does is reboot, which means the startup software is corrupt. Anyone know how to totally clear this phone so I can install the Rogers software and hopefully save it. Any help would be appreciated
Thanks Jeff