I don't know of anything that will run on Windoze Server 2003 that will act as an access point unless you want to setup an ad-hoc network which has no access points and everyone connects to everyone else. Depending on what you're trying to accomplish, ad-hoc may be adquate.
Some of the older Orinoco drivers have a registry key called "APMode" that allows the driver to simulate an access point, but that probably will not run on Windoze Server 2003. I suspect that even if you could find an AP spoofing program, you might have driver difficulties with an internal PCI card. I don't think any of the card vendors even support Windoze Server 2003 for their drivers although I'm fairly sure that the XP NDIS5 drivers will work.
Ah, it's the challenge. I see...