How to change username?

@rajeev075 (1936)
India
February 19, 2011 4:40am CST
I had window operating system and i want to work on the Linux too and grab some knowledge of it as well as for my course purpose. I did by taking vmware from my senior and he had created his name in the username of the vmguest operating system and i want to change the user-name to mine. How will i do that? I am able to change the password by passwd command but how to change the user-name?
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