Hi, and welcome to JustAnswer! My name is XXXXX XXXXX X am excited to get started with you.
Press and Hold the power button for 10 secs until unit powers off.
It is safe force shut down
If that does not work, Let me know so we can try other options
Yes but we will need to reset the PRAM first
1.Shut down the computer.
2.Locate the following keys on the keyboard: Command (⌘), Option, P, and R. You will need to hold these keys down simultaneously in step 4.
3.Turn on the computer.
4.Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears. Let computer chime 4 times
Where is it locked up at? Does it load to your desktop or stuck on the apple logo ?
Have you received a storage warning that your start up disk is almost full in the past?
What operating system are you running?
Its ok. We may or may not need the installation disk. We are first going to try to isolation your issue by fist removing all peripheral devices. Can you force shut down your computer and disconnect your external hard drive and other connected devices. Then power back on your machine
there may be an issue with your external drive. How old is your drive?
You can go ahead and restart your computer again just to make sure your issue is resolved
If you are satisfied, you can go ahead and accept my answer and end the Chat. You can also get back to me anytime you want even after rating at http://www.justanswer.com/computer/expert-michelleblack/.Enjoy the rest of your day :)