Personal Opinion on NT 4.0 AV would be Symantec Anti-Virus Corporate Edition 8.0. It has package rollout capabilities, Central Management (meaning scalable) and it incorporates Heuristics with Digital Immune System. Plus how can you beat the Virus response Team.

If not Symantec, Try Trend or Sophos, those companies at least have decent Virus Engineers and responses to Virus outbreaks.

My Opinion...Not that of the Man!