COMPLETED and FINISHED - what is the difference??

I was asked this by a student recently and had to ponder overnight for a perfect answer to give him.

The explanation that I have come up with is as follows:

Take an example of a young student who has been given some homework. He doesn't want to do it, he unwillingly has to. In this case if he is asked whether he has done his homework or not, he will answer, "Yes, I've finished it."

Say two people, Chris and Jim, broke their friendship up. When Chris tells other people about it, he'll say "I'm finished with Jim."

Yet another example, though a more gory one is when a murderer kills someone, and talks about it later, he says, "I finished him in his sleep." He would not say, "I completed him."

I believe that when you have no further intentions of doing a particular work, it is said you are finished with that task. There mostly is no happy feeling about being done with whatever it was.

Now think about you going to a bank to open an account. You are given a form to fill. When you properly fill up all the details in the form, you say, "I've completed filling the form up."

Let's again take the example of a young student, a studious one this time. When he's given homework to do, he cannot wait to do it and get the highest praise in the class for the same. When he goes to school the next day, he'll say, "Ma'am I've completed my homework! Can I submit the notebook to you?"

A third example is, when you end up watching all the seasons of F.R.I.E.N.D.S., you say, "I completed watching F.R.I.E.N.D.S.!! I'm gonna start with How I Met Your Mother now!"

We can conclude that when you finish the entire task given to you with satisfaction, it is complete.

There is usually a very thin line of difference between both words, but using both of them at places suitable for them makes you sound correct.

Let's see a joke I found on the internet while typing this article. If you aren't clear about the difference between both words by now, this will definitely do it for you!

"When you marry the right woman, you are complete. 
But, when you marry the wrong woman, you are finished. 
If the right one catches you with the wrong one, you are completely finished."
(Source: http://www.jumbojoke.com/whats_the_difference_between_complete_and_finished.html)