The Quake 3 Arena site has the Win32 server release of the Quake III Arena test release, which will allow you to run a server (only). Here's a local copy and mirrors of the 21 MB Q3ATest Win32 server. Here's the lowdown:

This version of the test allows you to run Win32 dedicated servers only. It does not let you play the test locally on the Win32 machine. We highly recommend Windows NT as a good stable environment for dedicated servers. Windows 95/98 will run, but will be prone to more problems.