How do I unlock a apple macbook OS X computer when I dont have the password?

Try asking the owner.

In the old days we kids used one specific jumper to remove parent's password lolz.

Yeah, or pull the battery for a minute.

That too Delroy, I forgot about that. Must have been something in the .... water.

Use the installation discs that came with your computer.

You can reset the password with them.

Go to an Apple Reseller and perhaps they can assist you.

Command + S on boot

Once in single user mode :
/sbin/mount -uw /
*RETURN*
rm /var/db/.applesetupdone
*RETURN*
reboot
*RETURN*

Now this will take you into the intro movie screen like the first day you booted your computer. Don't freak out, all you have done is removed the little tag that told your computer you finished setup, you have not deleted anything important. So you will go through the entire process as if you're computer were new and set up a New Admin account. With a new admin account you basically can change anything you want  .. hope this helps. Also this is a good reason to block shortcut keys on boot if you have a lot of people around your computer unattended.



CAUTION- BE careful in terminal. It is not a place to fool around if you do not know what you are doing.

Even I tried those codes:

Once in single user mode :
/sbin/mount -uw /
*RETURN*
rm /var/db/.applesetupdone
*RETURN*
reboot
*RETURN*

my macbook goes blank display after apple shows off.
Is there any solution?