Re: Update the firmware to original. Is it Possible?
Welcome to RobotC!
It is certainly possible to restore the original firmware back to the NXT. To do it, you use the software that came on the CD when you bought the NXT.
Before moving back to the old firmware, you would want to make sure you have a copy of the latest version of Lego's firmware. You can check for the latest firmware updates here
After you download the latest firmware, the zip file contains a readme that describes how to load the firmware back into the NXT. Here's a copy of what it says:
Of course, you can do this without downloading the latest firmware as well. Any versions of the NXT firmware that you have saved in the directory shown above will show up in the list and be available to send down to the NXT. Just follow the four steps at the bottom.