As this was my first Mac, I had done lots changes here and there to experiment and it was time to start afresh. Also I wanted to get rid of stupid packages and applications that I had installed in the past few years (including Xcode!)
When it comes to MS Windows installation I am an expert but in the Mac world I am hopeless.
Searched the Internet for ways to cleanup the hard disk and start a clean OS and saw different ways of doing it by different people.
The best way that works for me was:
- Press cmd+R and power on (You can also restart and do this)
- System goes into recovery mode
- Format the entire disk
- Install the OS from Internet
This saved me from creating boot disks, etc.