I am using Unity 4.0.0f7, and I want to update to Unity 4.1.
Do I have to uninstall the earlier version, and then install the latest version?
Please note that the computer in which I have Unity is not connected to internet.
You need to download it somehow. You can install without uninstall. You can install over the old one, or to a new folder, or on Mac, rename the old folder and install to default folder to have both versions available.
Make a COPY of your project before going to a new version of Unity, cuz you never know when it will do an ‘upgrade’ of your project, then something sucks in the new version, and you have no way to go back. So use your backup project.