Hi,
what's the SEPM version used?
this issue is fixed in MR 2 (refe release notes)
Windows 2000 Symantec Endpoint Protection clients appear as Unknown Computers in Symantec Endpoint Protection Manager
Fix ID: 1201891
Symptom: Running "Find Unmanaged Computers" from Symantec Endpoint Protection Manager finds Symantec Endpoint Protection Clients running on Windows 2000 as "Unknown Computers."
Solution: Correlated results of the Find Unmanaged Computers with the information already known about Symantec Endpoint Protection clients in the database to correctly identify Windows 2000 Symantec Endpoint Protection Clients.
Pete!