I had to reinstall the operating system on a Macbook A1278 – Mid 2009. I had to use this method because I couldn’t get the cmd + R keys to bring up the recovery mode.

If you experience the same problem then try the following:

Hold Cmd + S on start up. This will bring up a black cmd/dos looking screen.

type in the following:

mount -vw /
(press enter)

rm /var/db/.applesetupdone
(press enter)

shutdown -h now
(press enter)

The laptop will shut down. Turn it on again and it should start its factory restore process.

Check out the video below which helped me out.  Cheers CellularProz !