When are you going to bite the bullet? The network server is running MSWindoze Server 2003. So long as that computer is running MSWindoze, the business is gonna be like an immuno-compromised patient walking through a cholera-infested town.
There's no if's, but's, or maybe's about it. If you want security, Microsoft has to go. I suggest you replace it with Linux (it's superior in every way except for playing games as far as I know).