Is there a free way of unlocking an Android phone from a particular network? I bought a cheap Android handset for development and it is an exclusive to a particular network.

I would like to unlock it so I can use an existing SIM card from another network. I've done some googling and it appears that there are many services online where you can get a code from supplying your IMEI number.

Firstly, can anyone elaborate on what the unlocking process involves, and secondly, is there any application that can do this process, or are you forced to pay someone to generate a code for you?
To unlock you phone for free you can root it. But it is at your own risk. I found this guide but don't know if it works for you.