Always remember to DISABLE UAC (User Access Control) while installing Netbackup Server or Client on any Windows 2008 R2 Machine
As its mentioned in Netbackup Windows Admin Guide:
Note: To install NetBackup on Windows 2008/Vista and
Windows 2008 R2/Windows 7 UAC-enabled environments,
you must log on as the official administrator. Users that are
assigned to the Administrators Group and are not the official
administrator cannot install NetBackup in UAC-enabled
environments. To allow users in the Administrators Group
to install NetBackup, disable UAC.
How to disable UAC ?
4.Change User Account Control Settings