The reason you've been asked to completely uninstall the software is because the version you have is old and does not update properly with the new installation. Subsequent releases, you do not have to completely uninstall the software. You just need to install the later version over the prior.
Typically, your license will not be removed if you uninstall and reinstall the software. However, because your release is old, the license may need to be deactivated. If you run into an activation issue upon installing the newest release, please email techsupport@inteset.com with your order number and the issue will be handled. Please check your junk mail if you don't receive a response within a few hours.