Have you tried a local install of the Agent on the NT box?
Also From http://seer.support.veritas.com/docs/258576.htm
Windows NT 4.0:
1. If installing to Windows NT 4.0, verify Service Pack 6a is installed. This is the minimum system requirement for Windows NT 4.0.
2. If push installing the Remote Agent over the network to a Windows NT 4.0 computer, make sure a user with administrative rights is currently logged on to the Windows NT 4.0 computer. Also, when the Backup Exec installation program prompts for a user name and password to connect to the Windows NT 4.0 computer, enter the same user name and password for the user currently logged on to the Windows NT 4.0 computer.
3. If installing to Windows NT 4.0, verify Microsoft Windows Installer 2.0 is installed by typing "msiexec" at a command prompt.