Hey Tim,
There are some steps found in a thread by Shane_R linked below for how to do this type of generic driver installation.
To install a printer that doesn't have a driver for Windows Server 2003 in Windows Server 2003:
1. Connect the device to the computer. (USB)
2. Windows will try to find a driver but won't be able to.
3. Close any notifications that come up.
4. Click on the Start menu.
5. Click on Control Panel.
6. Make sure you have it set to Classic View.
7. Open the Device Manager.
8. Click on View and select Show hidden.
9. You should see a device on the list with a yellow triangle with an exclamation point in it.
10. Right-click on that device and select Install/Update driver.
11. A window will come up with 2 choices. Select "Browse my computer for driver software"
12. On the next window, select "Let me pick from a list of device drivers on my computer"
13. On the next window, make sure the check-box next to "Show compatible hardware" is not selected.
14. In the Manufacturer list, select HP.
15. In the Model List, select the Deskjet 990c driver or the Deskjet 450 driver.
16. Click Next.
17. Click Finish.
18. Try printing.
Let me know if this gets the printer connected and printing,
Jason