Log in to the Backup Server using your Backup Exec service account credentials.
Open the Windows Services Management Console (services.msc).
Review the Log On As user account listed for the Backup Exec services. This account will be needed later during the upgrade process.
Stop all running Backup Exec services.
Stop the SQL service hosting the Backup Exec database (SQL Server (BKUPEXEC64) or SQL Server (BKUPEXEC)).
Create a copy of the Data and Catalogs folders and store them in a safe location:
X:\Program Files\Veritas\Backup Exec\
or X:\Program Files\Symantec\Backup Exec\ (Note: X represents the drive letter where Backup Exec is installed).
If custom reports have been configured, back up the Reports directory:
X:\Program Files\Veritas\Backup Exec\Reports
Start the SQL Server instance service (SQL Server (BKUPEXEC64) or SQL Server (BKUPEXEC)).
Certain Windows operating system security policies block downloaded archive and image files. Unblock the file before extraction to prevent setup errors.
Unblock Procedure: Right-click the downloaded .zip file, select Properties, check the Unblock box, and click Apply. Repeat this process for the extracted .iso file if necessary, then mount the ISO image.

Open the mounted ISO directory in File Explorer.
Right-click Browser.exe and select Run as Administrator.

Important Notes regarding SQL Server (Backup Exec 22 and above):
- Upgrading to version 22.0 or higher deploys a 64-bit BKUPEXEC64 SQL 2017 Express instance. The legacy 32-bit BKUPEXEC SQL instance will be automatically removed near the end of the upgrade.
- If your existing Backup Exec uses a custom named SQL instance (anything other than default BKUPEXEC), the upgrade will retain that custom SQL instance and version.
In the DVD Browser menu, click Backup Exec

Review the software license terms, select I accept the terms of the license agreement, and click Next.
Select Install Backup Exec software and features (Local Installation) and click Next.

Allow the wizard to complete the Windows Server environment checks. Resolve any highlighted prerequisites before proceeding.

Enter your Entitlement ID or click Import License File (.slf).

If upgrading from a version earlier than v25 and you only have a license file for version 25, leave the key fields blank and click Next. A pop-up prompt will inform you that Trial Mode enables all options for 60 days. Click OK to proceed. You can import your permanent .slf license files after setup completes.
Enter the User Name, Password, and Domain for the Backup Exec Service Account (BESA), then click Next.

Advance through the wizard to the Migration step. Wait for the wizard to process and migrate configuration data.

Once migration completes successfully, review the summary report. Select I have read and acknowledge the changes in the migration report and click Next.

Setup will begin deploying prerequisite packages and Backup Exec core installation files.
When prompted, select Reboot system and click Finish. All pre-existing configurations will be retained upon reboot.
Upon reboot, if a Deduplication Storage folder is present, it will initially appear as OFFLINE.
Backup Exec will display an alert stating that Deduplication Storage conversion has started.
C:\Program Files\Symantec\Backup Exec\Logs\PDDE10 Conversion log

Once the log confirms completion ("Congratulations! The conversion has finished successfully!"), open Backup Exec Services Manager, enable deduplication services, and select Restart all services. Devices will come online.

Remote agents running on client servers must be updated to match the backup server:
C:\Program Files\Veritas\Backup Exec\Agents folder from the Backup Exec server.Agents\RAWS64 on the target server and execute setup.exe.This article provides step-by-step instructions to upgrade an existing Backup Exec installation to version 25.1. It covers prerequisites, database considerations, step-by-step setup walkthroughs, trial mode upgrades, and post-installation steps such as deduplication store conversions and remote agent updates.
Direct Upgrade Path: Upgrading directly to Backup Exec 25.1 requires a minimum starting version of Backup Exec 22.0. Step-by-step interim upgrades are not recommended.
Trial Mode Conversion: If you are upgrading from a version lower than 25.0 and only possess a license file for version 25, you can complete the installation using Trial Mode and apply your license key later.
SQL Instance Upgrades: Upgrading to Backup Exec 22.0 or higher automatically deploys a 64-bit SQL Server 2017 Express instance (BKUPEXEC64) to host the Backup Exec database.