how to delete the internal backup from my macbook pro

OS X does not keep internal backups. Please clarify what you're seeing.

Open the Terminal in the Utilities folder and enter or paste the appropriate command line. Press RETURN and enter your admin password when prompted. It will not be echoed.

To turn them ON: sudo tmutil enablelocal

To turn them OFF: sudo tmutil disablelocal

Note that turning them OFF will also delete all existing snapshots.

OS X Lion- About Time Machine's "local snapshots" on portable Macs

This worked for me really well. I simply restarted my Mac Air and all the local backup was gone..... :-)

Finally I got the empty hard disk space I needed since long .......