If a pre-15.10.10 version of TTU is installed then those products have to be uninstalled before installing 16.00. Any products installed separately from suites must be manually uninstalled.
If a 15.10.10 or later release is installed on the system then 16.00 can also be installed on the same system without uninstalling the 15.10.10 or later release. Please see MultiVersion Support for details.
If you need to reinstall v16.00, you must use Programs and Features to uninstall the existing instance of the product. For more information, see Interactively Uninstalling Teradata Tools and Utilities.