You're going to need to dig a little deeper then, because with both ATI and NVidia, they release one driver set for each operating system (that supports all their cards). So if you can't find drivers for the 2400 Pro, then all the ATI cards are going to be a problem for you (as an example).
Your problem is you're running a server OS, and almost all the cards are "consumer" cards. I found that the NVidia site actually has drivers for Server 2003 64 bit version, which are the same as the XP 64 bit version. But they don't list them for Server 2003. You might find that the XP drivers work for both NVidia and ATI.
Here's a link from EVGA's support FAQ, though:http://www.evga.com/support/faq/afmviewfaq.aspx?faqid=57764
So all I'd say is buy from a place with a good return policy!
You may also find the cards are supported out of the box (i.e. built into the OS).