How can I decode my Nokia N73 mobile phone?:D

This is how:

How to Unlock Your Nokia Cell Phone - wikiHow (http://www.wikihow.com/Unlock-Your-Nokia-Cell-Phone)

What is cell phone decoding? I always though locking or unlocking a cell phone meant if one didn't want to accidentally call someone on the cell phone when the phone was lets say in a purse they can lock the keys from being able to dial anything.

Nope, cell phones are usually locked by the carrier so that you cannot use the phone they give you with another company.

Why would a person get a cell phone and want to try to use it with another company when they are already going to get billed from the company they got the cell phone service contract with?

Well, just look at the Apple iPhone. You can purchase the phone without a contract, however, At&t has an exclusive contract with Apple. So, if you want to use the phone with someone other than At&t, you will need to decode/unlock it first.

Also, you could sign a 2 year contract with a carrier, and get an expensive phone for a reduced cost. But if you have a phone, and don't need it. You could sell the expensive phone to someone else, at a higher cost. They would need to decode your phone though, if they wanted to use another carrier.

Why would a person get a cell phone and want to try to use it with another company when they are already going to get billed from the company they got the cell phone service contract with?

You are like a 4-5 year old who asks why to every answer they get. Do you have any idea how annoying that is and how it puts people off?

I appreciate a thirst for knowledge, but not when taken to the extremes that you have.