# Installing Run-time Environment With or Without Legacy Drivers

On a Windows platform, Sentinel LDK Run-time Environment (RTE) is automatically installed either with or without legacy drivers, depending on the factors described below.

>Without Legacy Drivers

When the RTE is installed on a new machine, then by default, the installation does not include legacy drivers. This provides the most stable configuration of the RTE. Similarly, when upgrading the RTE on a machine where legacy drivers were not previously installed, the installation does not include legacy drivers.

>With Legacy Drivers

When the RTE is upgraded on a machine where legacy drivers were previously installed (for example, if RTE 8.15 or earlier was installed), then the installer keeps or upgrades these drivers. This ensures compatibility with existing protected applications.

You have the option of forcing installation of the RTE with legacy drivers on a new machine if necessary (for example, if you know that one of the situations described below exists). This can only be accomplished using the RTE command-line installer (haspdinst.exe).

Legacy drivers are required in following situations:

>When the application was protected using Sentinel LDK Envelope version 6.x or earlier AND the application uses the Version 1 data file protection mode to encrypt data. In this case, the legacy aksdf.sys driver is required.

>When the application is licensed using a Hardlock parallel port key or using a Hardlock USB key with a very old Hardlock library. In these cases, the legacy hardlock driver is required.

NOTE The hardlock driver is not supported by RTE 8.41 or later. If your application requires the hardlock driver, you must install RTE 8.31 or earlier.