Hiding IP address of my Desktop temporarily

I am working on a project and would like to hide my IP from the internet. I know there are several free software s available but I am worried a lot about malwares and spywares because the projects is very important and i do not want to get spied nor i can afford to lose data due to viruses. Please suggest the way to hide the IP only when certain user logs in. Also, if it is possible to do through the settings in windows it would be of great help! I am running windows 7 basic edition
