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 /
shutdown -h now
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 !