The two most common causes of failure with Backup Exec:
 

When Backup Exec is initially installed, logon credentials for the services and System Logon Account must be entered for the installation to complete. This account is required for the Backup Exec Services to startup, to be able to launch/use the user interface and for multiple other functions to operate properly.  If for any reason changes are made to this account or if the Backup Exec Installation is modified in an unsupported manner, Backup Exec may not function properly and jobs, updates, or upgrades may fail to complete with various errors. 

Listed below are steps that can be performed to resynchronize the Backup Exec for Windows Servers System Logon/Service account and installation, to potentially return it to the state it was in when the software was initially installed.
 

1. Browse to the C:\WINDOWS\Installer Folder.  Search for the file "BeInstParams.prm".  Rename this file to BeInstParams.bak.

Note:  If the Windows Installer Folder is not visible, change the folder options to make it visible (Tools, Folder Options, View:  select "Show hidden files and folders" and deselect "Hide protected Operating System Files").
 

2. In the Backup Exec Interface, go to Network, Logon Accounts.  Document which account (User name) is listed as the System Logon Account.  If there is not a System Logon Account showing under "Account Name", create one by clicking the System Account Button.
 

3. Confirm the account listed in step 1 has full administrative rights on the local machine and/or domain and is only a member of the administrative groups. Make sure the account also has the rights listed in the following document:
 

Requirements for the Backup Exec Service Account (BESA) https://www.veritas.com/docs/000028683

Logoff and back on to the media server with this user name and password.
 

4. Go back to Network, Logon Accounts.  Highlight the System Logon Account and then click the Edit Button.  Click "Change password" and enter the password that was used to log back on to the machine with.  Click OK.
 

5. Launch the Windows Services Applet.  Set all of the Backup Exec Services to "Log on as" the Local System Account.
 

6. In the Backup Exec Interface, click the Tools drop down menu and select "Backup Exec Services".  Click the Services credentials button.  Click "Change service account information" enter the credentials/password which matches that of the System Logon Account, then click OK.  Restart all the services.
 

7. Launch the Windows Control Panel, Add/Remove Programs Applet.  Highlight "Veritas Backup Exec for Windows Servers", then click the Change Button.  Click Next.  Select the Repair Option, click Next and allow the repair operation to complete.  If it does complete successfully, reboot the media server.
 

Note:  Veritas recommends that prior to performing an upgrade, all obsolete jobs, selection lists, policies, job history, media sets, logon accounts, etc... be removed first.  Veritas also recommends opening a case with Veritas Technical Support, rather than uninstalling and reinstalling Backup Exec if the information above does not resolve an issue, as better solutions may be available.