After a long search I found this and it works:
Approach A: (Arduino IDE/Arduino as ISP)
* Open IDE
* Tools >> Board >> Arduino Duemilanove 2009/Nano w/328
* Tools >> Serial Port >> (choose correct one)
* Upload the ArduinoISP sketch (Files >> Examples >> Arduino ISP) to your working NANO
(unplug your main/working Arduino Nano)
* Wire up your 'target' board that is outlined in the tutorials (D11, D12, D13, +5v, GND & RESET) pins...
MAIN BOARD: >>> TARGET BOARD:
D10: >>> RESET
D11: >>> MOSI
D12: >>> MISO
D13: >>> SCK
GND: >>> GND
+5v: >>> +5v
* Go to: Tools >> Board >> and choose ""Arduino Duemilanove 2009/Nano w/328"..
* Tools > Burn Bootloader > w/ Arduino as ISP
Yes good job. But keep in mine that you could have selected the Uno board type before the Burn Bootloader step. Benifits:
Handles watch dog timer interrupts correctly
Uploads sketches at twice the baud rate as the older nano bootloader
Smaller bootloader means a little more flash space available for larger sketches.
The only thing you have to remember is to always select the Uno board type before uploading sketches in the future, as your nano now thinks and behaves as a UNO board.