Realtek HD Audio Driver support all of Realtek HD Audio Codec in Vista/WinXP/Win2000/Win2003 .

So at least there is hope for Windows 2003 Server supports. However as I do not have a D945GCCR motherboard to test with, so I cannot guarantee it will work. Please try at your own risk.

Intel D945GCCR Windows 2003 Audio Driver Installation

1. If Windows 2003 Server auto detected the Multimedia Audio device and ask for the driver, please press the [Cancel] button.
2. Download the driver file AUD_allOS_5548_PV_Realtek.exe and run it.
3. Follow on screen instructions to continue the procedure. If the Windows popup [Digital Signature Not Found] message, press [Yes] to continue the installation.
4. Finally, select to restart the system and press [Finish] to complete the installation.
5. The system will reload the drivers and do some adjustments in the INF file if so required.

Additional Information on Intel D945GCCR Audio

1. Vista WHQL Supporting: ALC882, ALC883, ALC885, ALC888, ALC861VD, ALC660, ALC662, ALC260, ALC262,ALC267, ALC268, ALC269
2. Windows 2000/XP WHQL Supporting: ALC880, ALC882, ALC883, ALC885, ALC888, ALC861VC, ALC861VD, ALC660, ALC662, ALC260, ALC262, ALC267, ALC268, ALC269
3. HDMI Device WHQL Support: ATI HDMI Devices
4. Pack with Microsoft High Definition Audio UAAV1.0a(5013)

Fixes/Enhancement

1. Fix PC-Beep mute issue for ALC268/ALC267.
2. Fix the potential risk that system-thread is still running when driver is already unloaded under Vista.

Alternatively, you can try the Free Driver Scan.