The Raspberry Pi 2 is a massive upgrade for the Pi family. The new Pi is based on an ARM 7 processor whereas the old Pi’s are all based on ARM 6. If you don’t want to lose the hours spent on projects on your old Pi’s SD card then you will have to follow these upgrade instructions. As always it is important you backup your Pi’s SD card before making these changes. Click Here for a brilliant guide on how to do this.
To upgrade enter these commands into the terminal:
sudo apt-get update
sudo apt-get upgrade
sudo apt-get dist-upgrade
sudo apt-get install raspberrypi-ui-mods
Now put your SD card in your Pi 2 and enjoy!