Apple has released software that restores Intel Macs to their original factory condition, Firmware Restoration CD 1.1.
The 14.5MB update is used to restore the firmware of an Intel-based iMac (early and mid 2006), Mac mini (early 2006), MacBook Pro (early 2006), MacBook (early 2006), or Mac Pro (mid 2006) to original factory condition.
The software can only be used to restore the Firmware after an interrupted or failed update.
Users are required to download the software and to create a CD using the disc image. An installation guide and a download link to the software is available here.