VERITAS NetBackup 5.0 Installation Error

I have tried to install VERITAS NetBackup ™ 5.0 Pack NB_50_1A_M but have encountered an error during the installation. It gives the error message “Error 1920.Services vthost (vthost) failed to start. Verify that you have sufficient privileges to start system services.” Due to this, the system failed to install NetBackup Remote Administration Console with Global Data Manager Dashboard. Can somebody help me in fixing this error? I am attaching a screenshot of this error.
Any help would be highly appreciated. Thank you in advance.

