I have a 2 year old Mac book running whatever the newer OS X is. For some reason I was playing in activity manager and deleted launchd and now I'm just looking at a blank screen and my computer won't even shut down. Please help?
Hold down the power button for 10 full seconds.
If somehow that doesn't shut it down, just pull the power (both the AC power adapter and the battery, if your model has an externally removable battery).