When trying to install an agent it fails with the following error:
Computername Install 50 Computer type is not NT System:'\\Computername'
This is a native MS issue and the same error will occur if trying to manage the computer remotely, the error message is:
\\COMPUTERNAME cannot be managed because it is not running Windows NT
To reproduce go to "My Computer" - right mouse menu - Manage - Action - Connect to another computer and specify the computer name.
Sometimes a reboot of the affected workstation immediately resolves the problem.
The error occurs mostly with XP SP2 workstations and might also be caused by the following:
1. 'NetBIOS over TCP/IP' is disabled
2. "Windows Firewall/Internet Connection Sharing (ICS)" service is set to "Disabled", which leads to another known issue where the "Computer Browser" service times out and stops.
For more details please see MS KB article 889320: